This configuration works with the 5 monitors out of 6. I haven't added the 6th monitor yet but plan on it. My main concern at this time is in seeing the login screen upon entering the GUI.

Section "ServerLayout"
	Identifier     "X.org Configured"
	Screen      0  "Screen0" 0 0
	Screen      1  "Screen3" RightOf "Screen0"
	Screen      2  "Screen2" RightOf "Screen3"
	Screen      3  "Screen4" Below   "Screen2"
	Screen      4  "Screen1" LeftOf "Screen4"
	InputDevice    "Mouse0" "CorePointer"
	InputDevice    "Keyboard0" "CoreKeyboard"
	Option         "Xinerama" "true"
EndSection

Section "Files"
	RgbPath      "/usr/X11R6/lib/X11/rgb"
	ModulePath   "/usr/X11R6/lib/modules"
	FontPath     "/usr/X11R6/lib/X11/fonts/misc:unscaled"
	FontPath     "unix/:-1"
EndSection

Section "Module"
	Load  "dbe"
#	Load  "dri"
	Load  "extmod"
	Load  "glx"
	Load  "record"
	Load  "xtrap"
EndSection

Section "InputDevice"
	Identifier  "Keyboard0"
	Driver      "kbd"
EndSection

Section "InputDevice"
	Identifier  "Mouse0"
	Driver      "mouse"
	Option	    "Protocol" "auto"
	Option	    "Device" "/dev/mouse"
EndSection

Section "Monitor"
	Identifier   "Monitor0"
	VendorName   "DEL"
	ModelName    "DELL 828FI"
	HorizSync    30.0 - 64.0
	VertRefresh  50.0 - 120.0
	Option	    "DPMS"
EndSection

Section "Monitor"
	Identifier   "Monitor1"
	VendorName   "Monitor Vendor"
	ModelName    "Monitor Model"
	HorizSync    30.0 - 64.0
	VertRefresh  50.0 - 120.0
EndSection

Section "Monitor"
	Identifier   "Monitor2"
	VendorName   "Monitor Vendor"
	ModelName    "Monitor Model"
	HorizSync    30.0 - 64.0
	VertRefresh  50.0 - 120.0
EndSection

Section "Monitor"
	Identifier   "Monitor3"
	VendorName   "Monitor Vendor"
	ModelName    "Monitor Model"
	HorizSync    30.0 - 64.0
	VertRefresh  50.0 - 120.0
EndSection

Section "Monitor"
	Identifier   "Monitor4"
	VendorName   "Monitor Vendor"
	ModelName    "Monitor Model"
	HorizSync    30.0 - 64.0
	VertRefresh  50.0 - 120.0
EndSection

Section "Device"
        ### Available Driver options are:-
        ### Values: <i>: integer, <f>: float, <bool>: "True"/"False",
        ### <string>: "String", <freq>: "<f> Hz/kHz/MHz"
        ### [arg]: arg optional
        #Option     "SWcursor"           	# [<bool>]
        #Option     "HWcursor"           	# [<bool>]
        #Option     "PciRetry"           	# [<bool>]
        #Option     "SyncOnGreen"        	# [<bool>]
        #Option     "NoAccel"            	# [<bool>]
        #Option     "ShowCache"          	# [<bool>]
        #Option     "Overlay"            	# [<str>]
        #Option     "MGASDRAM"           	# [<bool>]
        #Option     "ShadowFB"           	# [<bool>]
        #Option     "UseFBDev"           	# [<bool>]
        #Option     "ColorKey"           	# <i>
        #Option     "SetMclk"            	# <freq>
        #Option     "OverclockMem"       	# [<bool>]
        #Option     "VideoKey"           	# <i>
        #Option     "Rotate"             	# [<str>]
        #Option     "TexturedVideo"      	# [<bool>]
        #Option     "Crtc2Half"          	# [<bool>]
        #Option     "Crtc2Ram"           	# <i>
        #Option     "Int10"              	# [<bool>]
        #Option     "AGPMode"            	# <i>
        #Option     "AGPSize"            	# <i>
        #Option     "DigitalScreen1"     	# [<bool>]
        #Option     "DigitalScreen2"     	# [<bool>]
        #Option     "TV"                 	# [<bool>]
        #Option     "TVStandard"         	# [<str>]
        #Option     "CableType"          	# [<str>]
        #Option     "NoHal"              	# [<bool>]
        #Option     "SwappedHead"        	# [<bool>]
        #Option     "DRI"                	# [<bool>]
        #Option     "MergedFB"           	# [<bool>]
        #Option     "Monitor2HSync"      	# [<str>]
        #Option     "Monitor2VRefresh"   	# [<str>]
        #Option     "Monitor2Position"   	# [<str>]
        #Option     "MetaModes"          	# [<str>]
	Identifier  "Card0"
	Driver      "mga"
	VendorName  "Matrox Graphics, Inc."
	BoardName   "MGA 2064W [Millennium]"
	BusID       "PCI:0:10:0"
EndSection

Section "Device"
        ### Available Driver options are:-
        ### Values: <i>: integer, <f>: float, <bool>: "True"/"False",
        ### <string>: "String", <freq>: "<f> Hz/kHz/MHz"
        ### [arg]: arg optional
        #Option     "SWcursor"           	# [<bool>]
        #Option     "HWcursor"           	# [<bool>]
        #Option     "PciRetry"           	# [<bool>]
        #Option     "SyncOnGreen"        	# [<bool>]
        #Option     "NoAccel"            	# [<bool>]
        #Option     "ShowCache"          	# [<bool>]
        #Option     "Overlay"            	# [<str>]
        #Option     "MGASDRAM"           	# [<bool>]
        #Option     "ShadowFB"           	# [<bool>]
        #Option     "UseFBDev"           	# [<bool>]
        #Option     "ColorKey"           	# <i>
        #Option     "SetMclk"            	# <freq>
        #Option     "OverclockMem"       	# [<bool>]
        #Option     "VideoKey"           	# <i>
        #Option     "Rotate"             	# [<str>]
        #Option     "TexturedVideo"      	# [<bool>]
        #Option     "Crtc2Half"          	# [<bool>]
        #Option     "Crtc2Ram"           	# <i>
        #Option     "Int10"              	# [<bool>]
        #Option     "AGPMode"            	# <i>
        #Option     "AGPSize"            	# <i>
        #Option     "DigitalScreen1"     	# [<bool>]
        #Option     "DigitalScreen2"     	# [<bool>]
        #Option     "TV"                 	# [<bool>]
        #Option     "TVStandard"         	# [<str>]
        #Option     "CableType"          	# [<str>]
        #Option     "NoHal"              	# [<bool>]
        #Option     "SwappedHead"        	# [<bool>]
        #Option     "DRI"                	# [<bool>]
        #Option     "MergedFB"           	# [<bool>]
        #Option     "Monitor2HSync"      	# [<str>]
        #Option     "Monitor2VRefresh"   	# [<str>]
        #Option     "Monitor2Position"   	# [<str>]
        #Option     "MetaModes"          	# [<str>]
	Identifier  "Card1"
	Driver      "mga"
	VendorName  "Matrox Graphics, Inc."
	BoardName   "MGA 2064W [Millennium]"
	BusID       "PCI:0:11:0"
EndSection

Section "Device"
        ### Available Driver options are:-
        ### Values: <i>: integer, <f>: float, <bool>: "True"/"False",
        ### <string>: "String", <freq>: "<f> Hz/kHz/MHz"
        ### [arg]: arg optional
        #Option     "SWcursor"           	# [<bool>]
        #Option     "HWcursor"           	# [<bool>]
        #Option     "PciRetry"           	# [<bool>]
        #Option     "SyncOnGreen"        	# [<bool>]
        #Option     "NoAccel"            	# [<bool>]
        #Option     "ShowCache"          	# [<bool>]
        #Option     "Overlay"            	# [<str>]
        #Option     "MGASDRAM"           	# [<bool>]
        #Option     "ShadowFB"           	# [<bool>]
        #Option     "UseFBDev"           	# [<bool>]
        #Option     "ColorKey"           	# <i>
        #Option     "SetMclk"            	# <freq>
        #Option     "OverclockMem"       	# [<bool>]
        #Option     "VideoKey"           	# <i>
        #Option     "Rotate"             	# [<str>]
        #Option     "TexturedVideo"      	# [<bool>]
        #Option     "Crtc2Half"          	# [<bool>]
        #Option     "Crtc2Ram"           	# <i>
        #Option     "Int10"              	# [<bool>]
        #Option     "AGPMode"            	# <i>
        #Option     "AGPSize"            	# <i>
        #Option     "DigitalScreen1"     	# [<bool>]
        #Option     "DigitalScreen2"     	# [<bool>]
        #Option     "TV"                 	# [<bool>]
        #Option     "TVStandard"         	# [<str>]
        #Option     "CableType"          	# [<str>]
        #Option     "NoHal"              	# [<bool>]
        #Option     "SwappedHead"        	# [<bool>]
        #Option     "DRI"                	# [<bool>]
        #Option     "MergedFB"           	# [<bool>]
        #Option     "Monitor2HSync"      	# [<str>]
        #Option     "Monitor2VRefresh"   	# [<str>]
        #Option     "Monitor2Position"   	# [<str>]
        #Option     "MetaModes"          	# [<str>]
	Identifier  "Card2"
	Driver      "mga"
	VendorName  "Matrox Graphics, Inc."
	BoardName   "MGA 1064SG [Mystique]"
	BusID       "PCI:0:13:0"
EndSection

Section "Device"
        ### Available Driver options are:-
        ### Values: <i>: integer, <f>: float, <bool>: "True"/"False",
        ### <string>: "String", <freq>: "<f> Hz/kHz/MHz"
        ### [arg]: arg optional
        #Option     "SWcursor"           	# [<bool>]
        #Option     "HWcursor"           	# [<bool>]
        #Option     "PciRetry"           	# [<bool>]
        #Option     "SyncOnGreen"        	# [<bool>]
        #Option     "NoAccel"            	# [<bool>]
        #Option     "ShowCache"          	# [<bool>]
        #Option     "Overlay"            	# [<str>]
        #Option     "MGASDRAM"           	# [<bool>]
        #Option     "ShadowFB"           	# [<bool>]
        #Option     "UseFBDev"           	# [<bool>]
        #Option     "ColorKey"           	# <i>
        #Option     "SetMclk"            	# <freq>
        #Option     "OverclockMem"       	# [<bool>]
        #Option     "VideoKey"           	# <i>
        #Option     "Rotate"             	# [<str>]
        #Option     "TexturedVideo"      	# [<bool>]
        #Option     "Crtc2Half"          	# [<bool>]
        #Option     "Crtc2Ram"           	# <i>
        #Option     "Int10"              	# [<bool>]
        #Option     "AGPMode"            	# <i>
        #Option     "AGPSize"            	# <i>
        #Option     "DigitalScreen1"     	# [<bool>]
        #Option     "DigitalScreen2"     	# [<bool>]
        #Option     "TV"                 	# [<bool>]
        #Option     "TVStandard"         	# [<str>]
        #Option     "CableType"          	# [<str>]
        #Option     "NoHal"              	# [<bool>]
        #Option     "SwappedHead"        	# [<bool>]
        #Option     "DRI"                	# [<bool>]
        #Option     "MergedFB"           	# [<bool>]
        #Option     "Monitor2HSync"      	# [<str>]
        #Option     "Monitor2VRefresh"   	# [<str>]
        #Option     "Monitor2Position"   	# [<str>]
        #Option     "MetaModes"          	# [<str>]
	Identifier  "Card3"
	Driver      "mga"
	VendorName  "Matrox Graphics, Inc."
	BoardName   "MGA 2164W [Millennium II]"
	VideoRam    4096
	BusID       "PCI:0:20:0"
EndSection

Section "Device"
        ### Available Driver options are:-
        ### Values: <i>: integer, <f>: float, <bool>: "True"/"False",
        ### <string>: "String", <freq>: "<f> Hz/kHz/MHz"
        ### [arg]: arg optional
        #Option     "SWcursor"           	# [<bool>]
        #Option     "HWcursor"           	# [<bool>]
        #Option     "PciRetry"           	# [<bool>]
        #Option     "SyncOnGreen"        	# [<bool>]
        #Option     "NoAccel"            	# [<bool>]
        #Option     "ShowCache"          	# [<bool>]
        #Option     "Overlay"            	# [<str>]
        Option      "MGASDRAM"           	# [<bool>]
        #Option     "ShadowFB"           	# [<bool>]
        #Option     "UseFBDev"           	# [<bool>]
        #Option     "ColorKey"           	# <i>
        #Option     "SetMclk"            	# <freq>
        #Option     "OverclockMem"       	# [<bool>]
        #Option     "VideoKey"           	# <i>
        #Option     "Rotate"             	# [<str>]
        #Option     "TexturedVideo"      	# [<bool>]
        #Option     "Crtc2Half"          	# [<bool>]
        #Option     "Crtc2Ram"           	# <i>
        #Option     "Int10"              	# [<bool>]
        #Option     "AGPMode"            	# <i>
        #Option     "AGPSize"            	# <i>
        #Option     "DigitalScreen1"     	# [<bool>]
        #Option     "DigitalScreen2"     	# [<bool>]
        #Option     "TV"                 	# [<bool>]
        #Option     "TVStandard"         	# [<str>]
        #Option     "CableType"          	# [<str>]
        #Option     "NoHal"              	# [<bool>]
        #Option     "SwappedHead"        	# [<bool>]
        #Option     "DRI"                	# [<bool>]
        #Option     "MergedFB"           	# [<bool>]
        #Option     "Monitor2HSync"      	# [<str>]
        #Option     "Monitor2VRefresh"   	# [<str>]
        #Option     "Monitor2Position"   	# [<str>]
        #Option     "MetaModes"          	# [<str>]
	Identifier  "Card4"
	Driver      "mga"
	VendorName  "Matrox Graphics, Inc."
	BoardName   "MGA G400 AGP"
	BusID       "PCI:1:0:0"
EndSection

Section "Screen"
	Identifier "Screen0"
	Device     "Card0"
	Monitor    "Monitor0"
	DefaultDepth 8
	SubSection "Display"
		Viewport   0 0
		Depth     8
		Modes      "1024x768" "800x600"
	EndSubSection
	SubSection "Display"
		Viewport   0 0
		Depth     15
		Modes      "1024x768" "800x600"
	EndSubSection
	SubSection "Display"
		Viewport   0 0
		Depth     16
		Modes      "1024x768" "800x600"
	EndSubSection
	SubSection "Display"
		Viewport   0 0
		Depth     24
		Modes      "1024x768" "800x600"
	EndSubSection
EndSection

Section "Screen"
	Identifier "Screen1"
	Device     "Card1"
	Monitor    "Monitor1"
	DefaultDepth 8
	SubSection "Display"
		Viewport   0 0
		Depth     8
		Modes      "1024x768" "800x600"
	EndSubSection
	SubSection "Display"
		Viewport   0 0
		Depth     15
		Modes      "1024x768" "800x600"
	EndSubSection
	SubSection "Display"
		Viewport   0 0
		Depth     16
		Modes      "1024x768" "800x600"
	EndSubSection
	SubSection "Display"
		Viewport   0 0
		Depth     24
		Modes      "1024x768" "800x600"
	EndSubSection
EndSection

Section "Screen"
	Identifier "Screen2"
	Device     "Card2"
	Monitor    "Monitor2"
	DefaultDepth 8
	SubSection "Display"
		Viewport   0 0
		Depth     8
		Modes      "1024x768" "800x600"
	EndSubSection
	SubSection "Display"
		Viewport   0 0
		Depth     15
		Modes      "1024x768" "800x600"
	EndSubSection
	SubSection "Display"
		Viewport   0 0
		Depth     16
		Modes      "1024x768" "800x600"
	EndSubSection
	SubSection "Display"
		Viewport   0 0
		Depth     24
		Modes      "1024x768" "800x600"
	EndSubSection
EndSection

Section "Screen"
	Identifier "Screen3"
	Device     "Card3"
	Monitor    "Monitor3"
	DefaultDepth 8
	SubSection "Display"
		Viewport   0 0
		Depth     8
		Modes      "1024x768" "800x600"
	EndSubSection
	SubSection "Display"
		Viewport   0 0
		Depth     15
		Modes      "1024x768" "800x600"
	EndSubSection
	SubSection "Display"
		Viewport   0 0
		Depth     16
		Modes      "1024x768" "800x600"
	EndSubSection
	SubSection "Display"
		Viewport   0 0
		Depth     24
		Modes      "1024x768" "800x600"
	EndSubSection
EndSection

Section "Screen"
	Identifier "Screen4"
	Device     "Card4"
	Monitor    "Monitor4"
	DefaultDepth 8
	SubSection "Display"
		Viewport   0 0
		Depth     8
		Modes      "1024x768" "800x600"
	EndSubSection
	SubSection "Display"
		Viewport   0 0
		Depth     15
		Modes      "1024x768" "800x600"
	EndSubSection
	SubSection "Display"
		Viewport   0 0
		Depth     16
		Modes      "1024x768" "800x600"
	EndSubSection
	SubSection "Display"
		Viewport   0 0
		Depth     24
		Modes      "1024x768" "800x600"
	EndSubSection
EndSection