Keyclone supports dual monitors set up in horizontal span, but not dual view (which if you are running XP is not worth using when gaming). I run 2 22"s just fine.

I dont know what rez a 20" does (I imagine 1600x1200), but I do 1680x1050 with 4 WoW's on it, and when I need to manually do something on one of the small WoW's, I cna still get it done. If you only have one monitor, going 4 in the background, and having 1 big overlap as your main would seem quite nice.