All of them. Eh you're just going to have to wait till it's launched to find out. Don't be surprised if it uses 350W or more. After all, an overclocked 6990 can use more than that if it's power tune limit is raised. We'll just have to wait and see.
I'd say none I realize I'm not answering ya question and I don't mean to be a weisenheimer ...... but consider this.
....if it performs as well as the 6990 did compared to the 6970 and 6950 (same for the 590 and the 580, 570, 560) I couldn't ever make a case to install one ..... two of the single GPU cards which would be cheaper and produce comparable or higher frame rates.
Guru3D uses the following games in their test suite, COD-MW, Bad Company 2, Dirt 2, Far Cry 2, Metro 2033, Dawn of Discovery, Crysis Warhead. Total fps (summing fps in each game @ 1920 x 1200) for the various options in parenthesis (single card / SL or CF) are tabulated below along with their cost in dollars per frame single card - CF or SLI:
So one 6990 for 762 fps at a cost of $725 or 95 cents per frame ..... two 6950's for 759 fps at a cost of $480 or 63 cents per frame or two 6970's for 825 fps at a cost of $640 or 78 cents per frame ????