tboo,
Can't help you with SLI, but the ASUS Commando has 2 x16 PCI-E slots and 4 PCI slots, where 2 of the PCI slots can be left open with 2 GPUs installed in the PCI-E slots - the PCIs are on the CPU side of the 2 GPUs. You'd have to get a couple of Crossfire cards to use it, though.
Would be interested to know if there are any boards that meet your requirements. PCI slots are becoming a rare commodity.
Noel