AFAIK, the ASUS P6T7 WS Supercomputer, has four PCI-e lanes, all at full 16x thanks to two NF200 controllers. Four-way SLI was never supported before, because nVidia graphic cards has never been able to support four graphic cards in SLI, apart from EVGA's own GTX 285 Classifieds. They have supported quad GPU SLI in the form of 7950GX2, 9800GX2 and GTX 295 in SLI.
I'm supposing the P6T7 has only been announced as four-way SLI with a BIOS update because recently the GTX 470 and 480 have been announced as four way SLI capable.
I can confirm that it works !!! I'm just using 4-way SLI with 4 480gtx on a P6T7 Asus Supercomputer Motherboard. You need the 4-way bridge from EVGA. And what is even more perfect is that I just took out my classified 4-way SLI Board as I had tons of Bluescreens (IRQ not equal....).
The Asus P6T7 is rock solid and stable....and was on the market way before the 4way classified. I just love my good ol' P6T7.
^X58 is your best bet! Forget about what people say about the platform..even though I have a sb rig..I would switch it for a 1366...it has most of the motherboards I want with the features I want..and unlike some people..I have no problems being stuck with a "dead" socket..besides...more processors are being made for the platform (995X/1000x -tentatively titled)...so I would get an x58 board..or wait