PCIe SLOT SPLITTER--
They go for $35-40 now. It is powered, and the graphic cards must be also by a powered USB riser and possibly a PCIe power line depending on the graphic card model.. There are models of this splitter card that sell for more than the price of a motherboard, too. Good luck! --scryptr
Something like:
http://amfeltec.com/products/flexible-x4-pci-express-4-way-splitter/