I think thats the second link I've seen that has suggested 60-70W higher power usage from a 680gtx, which isn't surprising considering the seeming overclock. I would think this card was aimed at similar TDP to a 560ti, maybe a bit higher but when they realised it could overclock higher they whacked it up.
From a lot of results though the 7970 overclocked to use similar levels of power would likely beat the 680gtx basically across the board.
FarCry2 25 fps down in max framerate, but only 2fps down in mins, if you overclock the 7970 by 25% , probably still use less power, you'd have same max and 20% higher minimums.
AvP is already ahead, at similar power levels the 7970 will spank it, Mafia 2 similar situation, slightly behind, at similar power levels it will blow it away.
You're looking at realistically underclocked 7970 giving Nvidia the chance to overclock theirs and beat it, the actual underlying core, 680gtx slower, 7970 faster, daft clock choices by AMD. 7980 with 1100Mhz clocks, lower power, faster than the 680gtx, significantly higher at higher res.