4GHz isn't uncommon on a quad, with air it just runs very warm - anything over 460x9 is very special, but not unheard of. To hit 500x9, I think you'd need just the right combination of "golden" parts. Some of these extreme guys on XS will actually remove and fit 'blueprinted' surface mount components to maximise their overclocks, and then there's voltmodding of course...
