Apevia is known to be fecal. Every one of them that jonnyguru ever tested was overrated, and most burned or melted.
Thanks, jsc, for providing the link that shows the 500W Antec Basiq is solid. In this application, it still may not be quite enough though.
Many PSU calculators overstate requirements because they are trying to compensate for all the overrated crap out there (e.g. Apevia).
Antec, Corsair, Seasonic, PC Power & Cooling, and Enermax are among the quality brands. OCZ isn't crap, but is far below that level. I've been reading commentary in a number of places recently that indicates they've been cutting corners on component quality. I wouldn't necessarily replace one in a working system (unless it was getting old), but I wouldn't buy one either.
Definitely choose one with full range active PFC (no little voltage switch) and 80+ certification.
And, a single HD5770 will run on a 380W Antec Earthwatts.