FSP is a decent brand. Only 400W though, with 27A on the combined +12V rails...I'm not sure that's quite enough, not for overclocking those parts.
Making arbitrary assumptions about your system, I got 363W using a NON-overclocked 4850. Stock, it needs 9A, so overclocking probably adds 1A-2A to that, or 12W-24W. It looks like technically that PSU could handle it, but you'd be running on the edge, which is asking for trouble. I don't think I'd do it.