Nvidia 5600/5700 or ATI 9600 should do the job. Not sure about US prices but they should be < $100. $125 for the 5700. I'm sure someone on here with those cards can let us know how they perform.

The older ATI cards like the 9200 sound like they have compatability problems with the game and avoid the 5200's if you can. They're cheap, but a tarted up GF2 is still a GF2 :)