Is their a big difference visually and performance-wise in the 295 vs the 260? If so what?
No, their about the same. bit-tech.net | Review - Nvidia GeForce GTX 295 1,792MB & Quad SLI (don't confuse the quad sli with the single gtx295)
In the build I posted you could switch over to 2 gtx260 c216 if you wanted to. Would probably be a little cheaper actually. Going with the 295 gives you the option for quad sli later but thats just a little crazy anyways.