NVidia 9800GTX/250, 260.
Ati 4850/4870, maby a used 4890 (massive uppgrade for the money, u should be able to get a slightly used one for arround $160-170 )
All cards can run most games on high or max.
P.S. 4890 really isnt in the same cathegory as the rest but are u considering used cards that would be a good bet. Was inches away from uppgrading from my 9800GTX to the 4890 a couple of weeks ago but my hous decided it needed a new waterpump

$2500 down the drain, litterally