The motherboard has only 5 pcie slots, so my guess is the maximum it can reach is 5 cards, I would invest a little bit in a better motherboard that supports more cards and more ram, you're going to pay like a 100$ more but it will save you more in the long run. The GPUs are good, although if you're in the us you can probably find better deals than this, for the PSU you'll have to either get 2 golden/bronze evga 750w (these are quite cheap, the bronze is only 60$ or so on Amazon) or get a 1000-1200w gold/platinum, evga is reliable and pretty cheap.