pistolpower: Considering that the 9600gt only has 64 stream prosessors you would probably be better of with a 9800gt as it has 112 stream processors which is 2x the processors 9600gt have on there pcb which would perform alot better than 9600gt. The 9600gt is $170.78 on pricespy whereas the 9800gt is $220.75. Both the 9800gt and 8800gt are better than the 9600gt which only has speed going for it. But if you wanted to get more serious then the next step up would be a 9800gtx+ which has hardly any more stream processors than the 9800gt but has faster clock speeds. But for $459.56 you get a gx 260 which has 192 stream proccessors which is almost 2x that of the 9800gt!!!! and 3x that of the 9600gt!!!!!! and it allso boasts over 700mb ram on it which is more than any of the other cards i listed!!! and its faster!! :D
Anyways go look on the nvidia website under "products" as they have rated there new 8,9series gfx cards in terms of performance by assighning them a number (use this to compare there performance then look at the price on pricespy) but i advise against buying the 9600gt as you should at least get a 9800gt because of the extra stream processors...
He has already chosen and purchased the ATI 4870 which is about on par with the 9800GTX. Recently Nvidia put in some significant price drops so now the 9800GTX is actually cheaper (wasn't before), however its still a solid option.