Internal Power

what internal power supply should i get for a costum built pc?
Im building a pc probably with either 2 gtx 260i or 2 9800 gtx’s but what power supply. 800w? 900w? 1000w? 1200w? And whats a ggod brand out there.
You’re gonna need at least 900W, OCZ and it’s sister companies are very reliable, and I think some ULTRA’s have a lifetime warranty.
Internal Power In The Martial Arts