Nvidia's GeForce 7800 GS chip is very good. I picked BFG's iteration at a local CompUSA for $380 dollars (after tax) but have seen it on sale at Best Buy for $250.
It's fast hell in games and runs very cool; my card doesn't ever break 42 degrees Celsius. The BFG card is also slightly overclocked (400MHz and 1250MHz on the GPU and memory respectively) from the default 375MHz and 1200MHz. Just make sure you have at least a 400-watt PSU if you pick one up.