The Core i5-3570k doesn't really use an excessive amount of power even when overclocked. The Radeon HD 7770 doesn't really use much power either compared to higher end cards; about 77w peak.
A 500w PSU will be more than enough for your setup. If you are trying to save some extra cash why not select the other Corsair 650w PSU I mentioned for $50? PSUs manufactured by CWT are still very good. If you are worried about power consumption, then regardless how much power a PSU can provide, the PC will only draw as much as it needs + wasted electricity due to inefficiencies. Therefore, the PC will basically draw the same amount of power from any 80PLUS rated PSU of any wattage. Naturally it's not a good idea to select a PSU that cannot provide enough power to the PC. That would be a bad thing.