You're questioning Seasonic, the maker of some of the best power supplies available for purchase and the base models for numerous other companies that sell psu's like Corsair, XFX, Antec, etc, and then link to a Seasonic X650?
The Seasonic X series is one of the most well reviewed power supplies with superb quality and conservative ratings on how much it can output. A Seasonic X650 is capable of putting out well over 900w's on the 12v rail without any problems and is capable of powering any and all sli / crossfire configurations.
Get it and enjoy it.