Guru3D uses the following games in their test suite, COD-MW, Bad Company 2, Dirt 2, Far Cry 2, Metro 2033, Dawn of Discovery, Crysis Warhead. Total fps (summing fps in each game @ 1920 x 1200) for the various options in parenthesis (single card / SL or CF) are tabulated below along with their cost in dollars per frame single card - CF or SLI:
The 560 is a bit of an unusual card.....while EVGA's new "Classified" gives 4 - 6% out of the box over the reference 580 card, simiular to what we see on the 6950. The 560 OTOH comes factory OC'd by as much as 15%.....2.5 times as much The robust voltage control circuitry and over size cooling make it easily overclockable to 1000MHz.
The reference 6950 (800MHz) comes in at 479 fps in the above test at 1920 x 1200 whereas the Frozr (850 MHZ) gets up to 484 in single card config. This jumps to 751 and 759 in CF.
The reference 560 (822MHz) comes in somewhat behind at 455 fps in the above test at 1920 x 1200 whereas the 900MHz versions gets 495 in single card config. This jumps to 792 and 862 in SLI.
The 900 Mhz versions are oft found at the same price. In order of performance.....