I tried the dual desktop thing for awhile...It didn't suit my needs.
Gaming while trying to record, encode, and playback tv was too much.
Now I just use 2 computers.
Left computer = Gaming (main computer)
Right computer = Media Box (that screen also has the wii attached)
Those are 32" 720p HDTV I use as monitors.
And just out of frame to the right is the girlfriends desk with her own computer.