Doom 3 with 4xAA and 8xAF
id Software Doom 3 with 4xAA and 8xAF

Notes
Running at 1024x768 with anti-aliasing and anisotropic filtering is roughly equivalent to bumping the resolution up to 1600x1200, it seems. Performance is still playable with a single 6600 GT, but even more so if you use a pair or get a 6800 GT. Again, ATI isn’t able to muster more than twenty-something frames on average.