just save up and get an 8800 gt. i bought that card and dont regret a second, cod4 runs smooth on maxed graphics (i think they're maxed) except for AA; its great. The price may drop soon w/that new card that was released recently.
I bought an 8500gt... yes I did. It was $60 on newegg so I was like "why not?". It wasn't bad but it wasn't for gaming. Sure I could play crysis at all low and still lag, it was good enough for CS:S, eve online, and bioshock. Pretty much unless your going to get an ATI 3850 or 3870 or an 8800gt, dont bother at all. The 3870 or 8800gt 512mb editions are the best bang for your buck and price/performance wise are tough to beat.