use your first setup with 8 gpus, but not the hd6 crap, put some nice HD5850 on it, expinsive but powerfull, 2 good PSUs with 800-850W and it will be fine.
It will give you about 2,9Ghash

And btw, why have you choosen such expensive boards with full 16 physical lanes per pci-e slot? there are much cheaper boards with just 2 or 3 pci-e 16x slots and a few pci-e 1 slot.
Its better to go for the cheap ones, as you surly know, the amount of lanes doesnt matter per slot.