6950 and it'll play crysis at 1080p. for more modern games check the game-related benchmarks (like the ones for BF3, skyrim, crysis 2 DX11, Rage, etc.).
rest of your system is fine.
p.s. if you're thinking of a crossfire setup in future then stick with the p67/z68. 2 6870s will handle 1080p with ease.