Based on my assumptions about fans and other devices, the PSU calculator at http://www.extreme.outervision.com/PSUEngine still showed <500W for your rig. Allowing for even more margin, something like a 550W XFX PSU would be good for that build.
Nope, it doesn't. With overclocking and capacitor aging thrown in, it just hits 501W, with 451W minimum. As good as the Seasonic-built XFX is, I'd be confident in it. Oh, the other two are also good PSUs, but over 600W is simply not needed.