Comment 4 for bug 473114

Well, I dont' know if you solved your problem with the xorg-radeon driver, but after working out the xorg.conf file, my monitor displays a perfect resolution.
Here is my xorg.conf, maybe it could help you if you haven't figured a solution yet.

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

Section "Files"
EndSection

Section "Module"
 Load "glx"
EndSection

Section "Monitor"
 Identifier "PLE2407HDS"
        HorizSync 29-81
 VertRefresh 55-76
 Option "VendorName" "IVM"
 Option "ModelName" "PLE2407HDS"
 Option "DPMS" "true"
 Option "PreferredMode" "1920x1080"
 Option "TargetRefresh" "60"
 Option "Position" "0 0"
 Option "Rotate" "normal"
 Option "Disable" "false"
        Modeline "1920x1080" 148.50 1920 2008 2052 2200 1080 1084 1089 1125
EndSection

Section "Device"
 Identifier "Default Device"
 Driver "fglrx"
EndSection

Section "Device"
 Identifier "amdcccle-Device[1]-0"
 Driver "fglrx"
 Option "Monitor-DFP2" "PLE2407HDS"
        Option "NoDDC" "true"
        Option "IgnoreEDID" "true"
 BusID "PCI:1:0:0"
EndSection

Section "Screen"
 Identifier "Default Screen"
 DefaultDepth 24
EndSection

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