If you're looking for DX11 support I'd go with the 5770. If you're not I'd get either a 4870 or a 4890. The 4870 runs a bit faster than the 5770. And the 4890 would be a bit better than both but it won't have DX11 support.
5770 for DX11
4870/4890 for a tad but more performance
What resolution do you plan on playing on?
Posted via RS Mobile