A GTX 560 factory overclocked to 950 mhz will be on par with a 6970. Many come overclocked to 900 mhz, and a couple are clocked at 1000 mhz. Since most 6950's are sold at reference speeds, and most GTX 560's are factory overclocked, the strategy should be to look up reviews of specific versions of the GTX 560. Like the Zotac GTX 560 AMP! card for example: