If you have the cash that card won't dissapoint! A personal recommendation is to get the 7950GT. Newegg has an evga for 215.99 (209.99 after rebate). Since I'm limited to AGP I have the 7800GS and it runs most every game (except oblivion) max. The 7950GT will blow mine away.
i went from a 6600 le to a 7900 gs and it blew me away. then the fan just blew and a rma later, ill have a 8800 gts. i liove evga, but i dont like there cooling solution on there 7900 series. a little bit more and you could have a 7950 with 512 mem instead of 256. i think the bfg on newegg is on sale right now. 8) scratch that the evga is really cheap and they have a 90 day step up. the new 8 series mainstream come out you could step up. :wink:
I didn't exactly upgrade from a 6600GT to a 7900GS , I upgraded from a Gigabyte Dual 6600GT to a Leadtek 7600GT. I saw a little bit of difference. I think I didn't see much differnece as the 6600GT was with a dual GPU so I could run it as an SLI device. Still in your case I think you'd see the difference espacially if you'll be playing games which have require strong graphics !!
A 7900GS can be overclocked to perform somewhat closely to a 7900GT.
IF you can find a good deal on it, worthwhile upgrade.
Try to get one with an OC friendly, lifetime warranty (or at least a lifetime warranty).