This is just a personal opinion, and you definitely don't have to go with me on this. Instead of getting a 7900GT (though my brother has it; it's a dang good card), I'd get a X1800XT
. It has about the same stats of the 7900GT: 800 less shader ops. per second; ~6 extra GB/s of bandwidth. Plus, the main thing, it's almost $100 cheaper. You can use this $ to get an E6600, supposedly a really really good processor; or you could just save ~$100.
Or if you've got a little extra money to upgrade, you could
get an X1900XT 512MB
, which is way faster than both these cards for only $40 more than the 7900GT. 30000 shader ops. compared to the 7900GT's 10800, and ~46GB/s, compared to the 7900GT's ~42.
I always have to throw this in when comparing video cards for people; here's
a comparison of the 7900GT and the X1800XT, though I have already stated what are probably the most important facts. For $100 less, it should probably match up with or maybe even be faster than the 7900GT. You can change one of the cards to the X1900XT to see its stats if you want to.
I've always liked NVIDIA, and all of their card's I've bought have lived up to their expectations. I cannot say the same about ATI, because I've never bought one. I probably would buy one sometime, but for right now I can't (or at least don't want to) because I bought an SLI-ready board and am stuck with it for a while (though I'm not dissatisfied one bit).
Remember, this is just what I'd recommend. It looks to be for the better, but it's your money; you do whatever you want. Get some suggestions from others before deciding.