I run my 4 clones on a 24" (7600gt) iMac 2.16 coreduo system booted into XP via bootcamp. Works well for the clones, but might be tough to come up with a maximizer setup you like for running a main at the same time. Before I started 5boxing I was running 3 accounts under OS X 10.5 using Spaces and CloneKeys. It worked well for 2 but my framerate wasn't really great after I added the 3rd.

Not really a solution to your problems, but maybe some food for thought.

--Tot