In that price range you said, you can get decent mid end card.. Me, as BB said use AMD, im saying that too.. You can either get new AMD 6850, or if you get lucky, you might even find used 6870.. They are both 1GB DDR5 and 256-bit.. I have personally used 6870 some time ago and i was pretty satisfied with it.. Just one more time to say, its not high end gaming gpu, its a mid end card, but a very good one, dunno how hard core gamer you are, but they are able to run big amount of stuff on high/ultra details on some 15/20-ish fps..
