The brand of the PSU along with the amps would be a big factor in this.
 

Ok well thats good to hear!. I have a TX750w Corsair PSU so im good. Thanks guys.

750W should be good depending on how conservative your OCing is. The TDP of the 560 Ti is 170W without OCing so let's start there.
 
170W * 2 = 340W DC + 250W (max. rest of system) = 590W
 
590W DC / 720W DC (max on +12v) = 82% capacity at full load without any SLI 560 Ti overclocking.
 
With maximum overclocking, let's assume that TDP jumps to 225W, the max of the rated supply from the PCIe bus and PCIe power connectors.
 
225W DC * 2 = 450W + 250W (max. rest of system) = 700W
 
700W DC / 720W DC (max on +12v) = 97% capacity at full load when heavily overclocked.
 
You never want to continuously load electrical circuits beyond 80% of their rated capacity for safety and longevity. With your PSU, if it shorts out, that single +12v rail at 60A (OCP is higher), you're likely to nuke everything on that rail... mobo, CPU, mem, video cards, storage, etc. Don't risk it if you plan to OC significantly.
 
At stock clocks on the 560s though, you're good to go. Your CPU OC was factored into the 250W max usage for the rest of the system.
 
Finally, note that these are simply approximations. There is no way anyone can give you exact numbers. This is just a reference point for average systems.