Which mobo and PSU for R9 295X2?

I didn't find any riview about what mbo, CPU, PSU should I buy for these cards. I try to get some used 295X cards, 4 of them, and built a rig. It is enough to buy a mobo with 4 GPU slot? Or these X2 card use 2 GPU slot on mobo since these are double cards?
A Little help is needed.