each hd69900   is 375W thats 750 for 2
how can you add TWO 6950 or 6970 (aprox 140W each) to a Corsair HX950W power supply

more sales hype

I will also investigate in the possibility of adding two 6950 or 6970 to each rig, giving about 700 MHash/s more. (This will need a larger PSU)