Twisto Gopro :
How big should my power supply be for 780 sli?
Some people say 750w and others say 1000w
I got an i7-4770k too..
Atm i got a Corsair CX750w
Hi - See ko888 post above. The key factor is the +12v amps available. 65 +12v amps is recommended, more for OC.
The CX750 has 62 +12v amps. It is reasonable to assume if you have a "K" processor, you intend to OC.
Considering you are short on +12v amps to begin with, you should upgrade to a good quality 850w or greater PSU.
I might also suggest considering your current components being of a high end nature that you step up in
quality from a budget/entry level PSU such as the CX series.
If you post a budget, we can assist you in finding one.