It's gonna depend on your monitor
I had a 6800 XT, and it ran BF2 pretty well, no AA, on a 1440 * 900. You can forget about AA on anything you can currently buy, even out the discount bin. A 4650 would be a step up, and they don't cost much more than the shipping.
Might want to look at upgrading to at least a 4670 for about the cost of a modern game. What processor do you have? If it's a dual core around 2.5 gigs or so, the card would be a decent match
i got Intel(R) Pentium(R) 4 CPU 3.20GHz