Два монитора + xfce

может, стоит использовать гном, чтоб было как в гноме?

У меня именно так и работает, вот конфиг

Section "ServerLayout"

Option "Xinerama" "on" Identifier "layout1" Screen 0 "aticonfig-Screen[0]-0" 0 0 Screen "aticonfig-Screen[0]-1" RightOf "aticonfig-Screen[0]-0" InputDevice "Mouse0" "CorePointer" InputDevice "Keyboard0" "CoreKeyboard" Option "Clone" "off" EndSection

Section "Files" RgbPath "/etc/X11/rgb" ModulePath "/usr/lib/xorg/modules" FontPath "/usr/share/fonts/X11/misc" FontPath "/usr/share/fonts/X11/cyrillic" FontPath "/usr/share/fonts/X11/ttf" FontPath "/usr/share/fonts/X11/100dpi/:unscaled" FontPath "/usr/share/fonts/X11/75dpi/:unscaled" FontPath "/usr/share/fonts/X11/Type1" FontPath "/usr/share/fonts/X11/100dpi" FontPath "/usr/share/fonts/X11/75dpi" FontPath "/var/lib/defoma/x-ttcidfont-conf.d/dirs/TrueType" EndSection

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

Section "InputDevice" Identifier "Keyboard0" Driver "kbd" Option "XkbModel" "pc105" Option "XkbLayout" "us,ru(winkeys)" Option "XkbOptions" "grp:caps_toggle,grp_led:caps" EndSection

Section "InputDevice" Identifier "Mouse0" Driver "mouse" Option "Protocol" "auto" Option "Device" "/dev/input/mice" Option "ZAxisMapping" "4 5 6 7" EndSection

Section "Monitor" Identifier "aticonfig-Monitor[0]-0" Option "VendorName" "ATI Proprietary Driver" Option "ModelName" "Generic Autodetecting Monitor" Option "DPMS" "true" EndSection

Section "Monitor" Identifier "aticonfig-Monitor[0]-1" Option "VendorName" "ATI Proprietary Driver" Option "ModelName" "Generic Autodetecting Monitor" Option "DPMS" "true" EndSection

Section "Device" Identifier "aticonfig-Device[0]-0" Driver "fglrx" Option "VideoOverlay" "on" BusID "PCI:1:0:0" EndSection

Section "Device" Identifier "aticonfig-Device[0]-1" Driver "fglrx" Option "VideoOverlay" "on" BusID "PCI:1:0:0" Screen 1 EndSection

Section "Screen" Identifier "aticonfig-Screen[0]-0" Device "aticonfig-Device[0]-0" Monitor "aticonfig-Monitor[0]-0" DefaultDepth 24 SubSection "Display" Viewport 0 0 Depth 24 Modes "1280x1024" EndSubSection EndSection

Section "Screen" Identifier "aticonfig-Screen[0]-1" Device "aticonfig-Device[0]-1" Monitor "aticonfig-Monitor[0]-1" DefaultDepth 24 SubSection "Display" Viewport 0 0 Depth 24 Modes "1600x1050" EndSubSection EndSection

Section "DRI" Mode 0666 EndSection