A single 8800GTX can be run on a 400W FPS...SLI of them a 500w good brand can do it. To be on the safe side go with a good 600w or so. It doesn't have to be the most reputed company but still. Ste is right, Antec's PSU's are nowhere near the quality they use to be.
I would go with the Corsair 620HX to run that build as well but there are other PSU's that you can get as well that are trusted.
E6300 w/ Arctic Freezer Pro 7 @ 3.6ghz 1.4Vcore
Antec 900 Case
EVGA 750i FTW Mobo
4x1GB of G.skill DDR2-800
2 8800GT in SLI
22" Samsung Syncmaster
1 250GB WD and 1 Seagate 7200.10 in RAID 0
Corsair 520HX 3DMark06 Score: 13900