Don't worry.. if your PSU have a full 12v wattage line (620w in them), it delivers 51A.
This is enough even for a GTX 590 with a heavily OClocked i7.
Don't need to get a beefier PSU.
Let me guess.. this PSU is Antec Earthwatts 620w?
Actually this PSU is SeaSonic S12II 620w
Thanks to all of you guys..