well, a system
equipped with Processor
Intel Core i7-3960X @ 4.3GHz Motherboard
EVGA X79 SLIDisk Drives
Samsung 470 (256GB) Memory
G.Skill Ripjaws DDR3-1867 4 x 4GB (8-10-9-26)
and GTX 770
only consume 374 watt for total power consumption
and 383 watt while stressing with Furmark for total power consumption
So, any 500w+ good psu from well known brand (seasonic, corsair, antec, fsp, etc) more than enough to run your system...
if your psu is a good quality psu, then your 650w psu is more than you need..