I will say that I love this board, but I can't speak on whether or not it needs that kind of amperage. I have a 435W Enermax that I LOVE, and I'm sure it meets any power requirements.
However, when I upgraded to this board (just last weekend) I had to get a new case as well, and while I did not want a PS, I found the perfect case (lots of room for fans and hard drives) with a PS. So, as my friend was over and wanted to LAN with Warcraft III for awhile, I just went with the PS it came with. It was a cheap 350W PS from Turbolink that puts out 24A on the 3.3+V line. It ran for 6 hours without a problem. However, with my proc at full load, all 5 case fans, 5 hard drives, a burner and the HSF, I was taxing it quite a bit. The power supply got quite hot, so I decided that it was best to switch them out before I ran into problems. Therefore, I can attest to the fact that at least one K7S5A will run with a smaller PS. In fact, now that I think about it, I put together a system for a friend a year or so ago and he had a cheap PS with his. It's been running fine ever since. He has absolutely no complaints. Maybe some don't work so well, but I would bet that the rev 3 boards will run fine.