If you're gonna go for one then get a good one from whichever series. A geforce 7900 would outperform an 8200 =)
My GeForce 4 Ti easily beats a friend's FX5200, though the early FX cards were infamous for being shit.
Just get an 8800 or 8900 and you'll be set for ages. Also, in order of worst to best, GS -> GT -> GTX
GS cards are budget ones with features removed or they're slower, GT could be considered mainstream and the GTX ones are for nerds with big wallets who just want the most powerful available.
Try asking on this site, a friend of mine runs it:
http://geforce3d.net =)