PSU requirements for gtx 560 ti sli/6950 hd crossfire

[wuggi]

I'm getting a new gaming rig in a month or two and I'd like to know what kind of psu I'll need to run the following:

Gigabyte Gtx 560 ti oc OR some radeon 6950 (planning on getting a second card for sli/crossfire)
Intel Core i5 2500k, planning on doing some overclocking, but probably not beyond 4ghz
ASUS P8P67 PRO
8 GB corsair ddr3 ram 1600 CL9
1 tb 7200 rpm Hdd (probably some WD or seagate haven't decided on the specifics yet)
1 Dvd drive

 

[mosox]

750W to be safe.