1680x1050 - UberSampling Disabled
Having bruised our test rig's ego, we proceeded testing with UberSampling disabled. The performance change is beyond dramatic, as the previously crippled GTX 590 and HD 6990 delivered 83fps and 81fps at 1680x1050.
It was interesting to find that the GTX 580 and 570 are considerably faster than the Radeon HD 6970 and 6950. It's also worth noting that the HD 6870 and GTX 560 Ti offered similar performance, as did the HD 5830 and GTX 460.
As purists, we generally aim for 60fps, but we'll admit that 30fps is acceptable for playing The Witcher 2, and this achieved by the budget-oriented HD 6770 at 1680x1050. Likewise, the GTX 460 and HD 6790 averaged over 35fps.
For consistently smooth gameplay, you'll want to shoot for 40fps or higher, but even this only took the mid-range HD 6850 or GTX 560 Ti. The GTX 480 fell just short of 60fps while the GTX 570 was the first to breach our ideal at 67fps.