My X-fi would get squeezed out but yea they would fit
Actually the middle PCI-E slot is like a wee too close to the first and any card put in there would be only milimeters away from the 8800, which probably won't be a good thing. I believe next-gen cards are supposed to get smaller thanks to GPU shrinkage and that's what 3 and 4-way SLi would be made for perhaps.