Processor is i7-920 2.66, so don't see why i couldn't handle 560. I did have a question as to how much power would be needed for sli 560's. currently running sigma 1000w
1000 watt is more than enough. If i were to buy a new PSU i would shoot for 800-850 good/great quality brand to run 560 ti sli setup.
If you choose SLI in th 460/560 range, make sure you have enough 6pin cables.