This will do the math for you.http://www.antec.outervision.com/
As for what brands are good ....forget brands. It's the various lines within a brand that determine quality. You will want to pick from the 1st 3 groupings below if you are using twin GFX cards and OC'ing more than 25-30%.
Antec SG Series - "cream of the crop".....rated 10 in performance on jonnyguru and makes Editors's Choice list at http://www.silentpcreview.com/Recommended_PSUs
where you will also find the Seasonic X-650 and Enermax Modu82+ 625W
Antec CP Series - a mix here, while the 850 model gets a 10 at jonnyguru, the 1000 watter is only slightly more powerful than the 850. The CP-850 makes silentpcreview's Editor's Choice list.
Corsair HX Series - Equal to the Antec SG / CP series electrically but it's noise output keeps it off the silentpcreview EC listing....but it does make the recommended listing
Corsair TX / Antec TP / TPX Series - More than adequate for most builds including moderate overclocking.