I built a computer for a squaddie. Even with a strict $500 budget, I chose a 5770.
It turned out very nice. At 1920X1080 resolution It could take full AA, all settings maxed, hires (2048 textures), and even 4k shadows without ever dropping below 60fps. The only thing not enabled is other plane's shadows.
I personally use the 5830 which is only marginally better than the 5770, but I wish I had saved up more for at least a 5850.