You are right I just wanted to hear your opinion when I first saw it I thought
MMMM Quad SLI Hah the normal boosts about 30%to35% imagine what the quad SLI Just think one card 100% two of them 135% three 170% and four 205% so you pay 400% price for 205% over the single card NO THANK YOU
It doesn't look like they are using 7900GTX 512's for the setup. It looks more likely to be a proprietary 7900GT 256 setup. You have the same amount of RAM as in an standard 7900GTX 512 setup, with twice the pixel pipelines and GPU's to provide throughput. The best news about this is that there is a drive that will support Quad SLi with could be used with Asus or Gigabytes Dual GPU cards in an SLi configuration. So you could do it yourself, with a standard SLi Mobo. Albeit with lest Bandwidth than a true Quad SLi Mobo.
Regards,
P.S. As you can see from my signature, I am running a FX5900 Ultra. I don't even have PCIe, let alone SLi. So I have no vested interest in it, but it makes sense for performance because that is the way that processors are going. i.e. Parallel processing of lower clocked cores.