The Seasonic is definitely an excellent unit and I agree with everything ko888 said. It does pain me how expensive it is, though. Either of these will power your rig just fine for a fair bit less, and both are highly reputed/rated:http://www.newegg.com/Product/Product.aspx?Item=N82E16817139016http://www.newegg.com/Product/Product.aspx?Item=N82E16817139010
A *quality* 600w unit can run 2x 6950s stock, and a quality 700w unit can run them unlocked (not sure which versions) and overclocked to the max. Both of the above are quality 750w modular units.
Edit: Accidentally submitted too soon. Please excuse the unsolicited advice, and know that the Seasonic PSU is top quality:)