In the end the X58 chipset only has 36 lanes for PCIex, so none will be true 16/16/16. Most are setup to run 16/8/8 or 16/16/4. The Asus P6T, P6T Deluxe, P6T WS, and Rampage II Extreme all have it. DFI's T3eH6, Gigabyte's UD4P, UD5, and Extreme do as well. Other brands can do it as well, but your best options are those listed above. Since it's not possible to run 16/16/16, you might be better off running 2 powerful cards in SLI and a 3rd, cheaper card as your PPU. IE. GTX285/GTX285/9800GT (16/16/4). The benefit for the 3rd card in SLI is less than the benefit from the 2nd, since there aren't enough lanes for the card to deliver at full tilt.