I should have mentioned im not interested in the new GTX4XX cards, as a GTX460 costs $100 more than i can get a GTX275 for a little more performance, althought it has DX11 features and better power consumption things that im not really bothered about.
GTX 280 is the one you want, although I strongly suggest a GTX 460. The 460 might be $100 more, but it's much more future-proof than the older GTX 280. DX11 is already on several games, and it will really take off in 2011.