I don't see why it would be mistaken; the 580 has 1.5GB of memory. Two of them have 3GB. AMD simply chose to put 2GB on its higher end single GPU models, a decision which doesn't make a massive amount of sense until you game at really high resolutions and/or use Eyefinity.
I can't see how it can "only" do with two 8-pin connectors, not unless it's being significantly downclocked. I checked Anandtech's power readings for their 6990 review and the 6990 uses 130W less power than two 580s playing Crysis, and considering AMD throttle their cards for FurMark, the stock 6990 uses 300W less power in comparison (using the OC BIOS still results in 166W lower drain). The removable cover is a nice touch. All in all, this card isn't going to be cheap and I reiterate that I can't see it being fully clocked - hell, even the 6990 isn't all that.
22nd March is just next Tuesday so we don't have long to wait for answers.