Originally Posted by benfica
For GTX770 SLI I would go with a decent 750w Powersupply
That's overkill though:
With two GTX 770s under full load in their system, their PSU pulled 505W from the wall outlet. Their CPU was idling, so if I add 150W for an overclocked mainstream CPU (like Intel's K series for Sandy and Ivy Bridge and Haswell), then that makes the PSU pulling 655W while under full load. However, that's what the PSU is pulling from the wall outlet, not what the computer is pulling from the PSU. The computer would be pulling less due to the efficiency being less than 100%. So, if the PSU were 90% efficient while pulling 655W from the wall outlet, then the computer would be pulling 589W from the PSU, but the gaming power draw will be lower, topping out at roughly 550W. So, a good quality-made 650W PSU is more than enough. This excludes the Gold-rated Corsair HX650 because it only has 2 x 6+2-pin PCI-E connectors.