The standard was x amount of peak watts (150, i think) drawn from the PCIe slot, and y amount of watts from each aux power input (+150x2), for another 150 watts each, peak....; to require even more power would stray from the standard specs.
The problem is that they wouldn't make a card that could handle the power draw as it would have either been to difficult or wasn't going to be cheap. The vrm can handle more but remember early on "the way it was meant to explode" because they were so damn cheap the fuses often blew or worse the mosfets burned out when ocp and ovp didn't work properly and would surge up to 550w only to blow up.
This card is trash and wouldn't pay $100 for it because they are crap and the worst dual gpu card yet from nvidia. They can't even make enough of them to even matter for the ultra high end market. They also run a lot hotter than every thing else out there so why waste the cash?
6990 is a better built card but not all that great knowing how dual gpu cards usually fair after a few years but it is worlds better than the gtx 590 and uses much more efficient gpus than the GF110 Fermi. From the enginering stand point they shold have used a single cooler to cool both gpus and a mid plate that wasn't unified to the main cooler. Copper fins and a aluminum back plate that spanned the whole length of the card. They should have used thermal pads to help deal with the hot spots while the entire power vrm should have been redesigned. I wouldn't care if it were long hell they could charge $1200 for it and would buy it if they done it right the first time and people would have thought of it better than they do know. The gpus are simply held back far to much to be any where near their full potential. These are low watt low amp and low volt samples that are higher binned than normal and could easily overclock beyond normal retail cards. However they screwed it up but at least the 6990 is a decent product. I would buy the 6990 but it is a waste at the ress that I play at and usually never have the budget to get one but right now I do but rather kick the can down the road for 28nm based cards.