I dont have the power meter on me right now, can anyone give me a power usage of 280x (can be full pc) hashing at around 515Mhash/s with smelters?
A lot, actually - 1 computer w/ 1 280x card burns 260W
(I think my cpu burns around 70W)

That is pretty close to my figures, I have 2 - 280x and the entire rig pulls ~550 watts from the wall. I believe it draws ~ 50 watts idle, so I would say about 250 watts per card is pretty close.