You list a GTX280 but say you have sent it back, either way I would look to replacing that PSU first as it's mediocre at best.http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story4&reid=137
I'm looking into replacing that with a good corsair one, maybe the 750w one, though the review you showed me doesn't set it up in too bad a light, 8/10 aint bad. I live by mediocrity :P
How's the ATi 2GB XFX HD 4870 X2? Do you need a crossfire compatible motherboard to use it to it's full potential? I hear it has two processors in one, so would that mean i need crossfire?