4 3750s? I dont think so, and you could probably just hook 2 of these cards togethor, and have quad sli. Or in theory, a board supporting tri sli, could hook 3 of these suckers up, and even if you cant use them all for graphics, one of the dual cards could be used for physic or something. But it would be a complete waste of money.
And the 7950gx2 that was such a failure, is up there on the GPU charts at tom's hardware. Above the 8800gts 320mb.