It should be fine, but it also depends on what else you have in your rig.
Note that those are peak amperage, not constant, so you cannot simply add the two numbers to get a total. I would guess that total 12v amperage will actually be 33A to 35A.
According to the specs it will only ouput 30 amps combined on the +12v rails.
Should power an 8800GTS 512, but as was said, it depends on what else you have.