btw, the link you posted is with 3 GTX 280, not 285
In SLI or CF, the memory on the cards is mirrored, i.e. the total VRAM of frame buffer size remains the same (i.e. that of the card with the least VRAM)2 gtx 295s, no doubt, the gtx 285 core would have to be more than 30% faster than the cores in the GTX 295, also the two GTX 295s would equal a greater total frame buffer amount. the gtx 285s would run out of frame buffer first if the resolution and AA was pushed too hard.