I wouldn't reccommend an X800 period, although I hear the $500 range ones aren't that bad. Still, ATI has sucked the big one this generation. Go with the 6600GT. It beats all but the highest end ATIs and is great value for the money.
ur cpu should be fine for the gamesu want tbh. yes definatly try to get xp, (pro is better but home is ok) i would spend sum cash on that, just get the oem verison and then get 6600gt with wat u can afford left over, maybes the msi card cos that is one of the cheaper ones but it is still good.
I know, but the 6800 doesn't. I'm saying, throw GDDR3 into the 6800 and call it a 6600Ultra instead and it seems like it might be a fairly popular card.
ATI's aren't bad, in fact they are better than nvidia.