In the following tests, we're using the Medium detail preset, in addition to 2x anti-aliasing.
The Radeon HD 7770 delivers at least 30 FPS at 1680x1050, while the GeForce GTX 650 is a bit faster than that.
Running at a resolution of 1920x1080, AMD's Radeon HD 7770 drops under 30 FPS. You'd probably want to turn off anti-aliasing or drop the detail settings a bit to help improve performance.
In better news, the GeForce GTX 650, 660 and Radeon HD 7850 and 7870 have no problem maintaining smoother frame rates.