not for four 6990s you wouldn't, or at least I hope you wouldn't...lol
Sorry you're right, I wasn't paying attention to exactly what he was trying to run; I was on auto-pilot posting that after reading so many threads where people were asking what PSU to buy for their dedicated miners with 1-3 GPU's in each box. That link also has interesting graphs of efficiency vs load which will tell you how much to overshoot your power requirements by when picking a PSU.