Honestly, you're going to need to go with dual PSUs... there are a couple that could peak at 1800w or so, but none that are going to do that sustained. I'm assuming you'll be mining, you'll want two PSUs and enough headroom to not kill efficiency because I'm also assuming you pay for your own power. When you're doing that kind of sustained load, the efficiency really does make a difference in the electric bill.
But then if he's mining why not just buy an ASIIC? Last I heard they were starting to be finally be produced.