Th3Kaka :
So I am looking to buy a GTX 770 and I want to know what is cheapest power supply that supports GTX 770. (Gtx 770 needs 42A. 600W PSU)
That is not entirely right the GTX 770 has a TDP of 230 Watts (19.17 A )the rest depends on the rest of your PC parts being used.
The only real answer you can get is by listing all the parts used in your PC.
Also of course where you can buy parts from as to what is the best buy.