This works with the left and middle monitor on one video card.

working xorg.conf

Section "ServerLayout"
	Identifier     "amdcccle Layout"
	Screen      0  "amdcccle-Screen[1]-0" 0 0
EndSection

Section "InputDevice"

    # generated from default
	Identifier  "Mouse0"
	Driver      "mouse"
	Option	    "Protocol" "auto"
	Option	    "Device" "/dev/input/mice"
	Option	    "Emulate3Buttons" "no"
	Option	    "ZAxisMapping" "4 5"
EndSection

Section "InputDevice"

    # generated from default
	Identifier  "Keyboard0"
	Driver      "kbd"
EndSection

Section "Monitor"
	Identifier   "0-DFP4"
	Option	    "VendorName" "ATI Proprietary Driver"
	Option	    "ModelName" "Generic Autodetecting Monitor"
	Option	    "DPMS" "true"
	Option	    "PreferredMode" "1920x1080"
	Option	    "TargetRefresh" "60"
	Option	    "Position" "1366 0"
	Option	    "Rotate" "normal"
	Option	    "Disable" "false"
EndSection

Section "Monitor"
	Identifier   "0-CRT1"
	Option	    "VendorName" "ATI Proprietary Driver"
	Option	    "ModelName" "Generic Autodetecting Monitor"
	Option	    "DPMS" "true"
	Option	    "PreferredMode" "1366x768"
	Option	    "TargetRefresh" "60"
	Option	    "Position" "0 0"
	Option	    "Rotate" "normal"
	Option	    "Disable" "false"
EndSection

Section "Device"

#    BusID          "PCI:1:0:0"
	Identifier  "Device0"
	Driver      "fglrx"
EndSection

Section "Device"
	Identifier  "amdcccle-Device[1]-0"
	Driver      "fglrx"
	Option	    "Monitor-DFP4" "0-DFP4"
	Option	    "Monitor-CRT1" "0-CRT1"
	BusID       "PCI:1:0:0"
EndSection

Section "Screen"
	Identifier "amdcccle-Screen[1]-0"
	Device     "amdcccle-Device[1]-0"
	DefaultDepth     24
	SubSection "Display"
		Viewport   0 0
		Virtual   3286 1920
		Depth     24
	EndSubSection
EndSection