The 4770 requires one 6 pin pci-e connector. Pulls about 85 watts. Should be no problemo
edit: As long as you don't decide to run a o/c i5 750 with high Vcore. Everest shows my 1.40 v 4ghz 750 spiking over 200 watts
under prime95. Just showing a example of o/c systems using much more wattage than most think.