My system is almost identical to yours and same OC (someitmes run at 3.6, but don't need it yet), but with 1 more HDD than you and an 8800GT.
Under prime95 load and gaming it only pushes 295 watts.
I have a Seasonic 500watt.
You loose efficiency with modular PSU's at the connections, so I alwasy go hard wired.
They are all pretty good. I'd make one of my main deciding factors its efficiency these days.