Benchmark Results: 4x AA, DirectX 9
AA seems to tighten the playing field a bit. At 1280x1024, the Radeon HD 4650 is the only card that can't hack an average of 30 FPS, although it comes close.
At 1680x1050, most cards offer between 40 and 60 FPS, with the GeForce GTX 260 and Radeon HD 4870 standing out with similar 75 FPS performance.
Now at 1920x1200, there isn't a large change in the situation as all of the cards are performing a bit slower.
At the highest 2560x1600 resolution, only the Radeon HD 4870 and GeForce GTX 260 offer good (but not exceptionally smooth) gameplay. The rest of the cards are able to muster about 30 FPS or less.