i just checked and unfortunately xbitlabs isnt measuring the vga consumption anymore
they had really professional results modding the pciE slot on one board to meassure all the power that flows to the card... really a shame...

according to techpowerup the gtx 280 is 293W under load, well, system consumption, compared to 305W for a gx2.
the last vga power numbers from xbitlabs meassured the gx2 at 180W under load.

so the gtx280 consumes around 10W less than the gx2 which means 170W

tpu also reviewed the gtx280 amp edition from zotac, which is clocked at 700/1150 compared to 600/1100 of a normal gtx280 card.
it consumes 318W under load, which is almost 15W more than the gx2, which is at 180W according to xbitlabs.

sooooo the final conclusion, the oced gtx280 cards are already scratching on the 200W barrier!
im really curious if nvidia will really go for an ultra card... tdp wise it would make more sense to go for a dual card with lower clocked gpus...