Looks like I would need a 1300+ watt PSU. But I have read guys running a 6*1070 rig with 800W psu.
A single 1300W PSU costs a lot compared to 2*700W PSUs. But then I don't have any experience in mining.
I have one of my rigs running 8 1070s with a 1200w Platinum PSU. I have the GPUs undervolted and drawing ~100watts each for a total draw from the wall at ~950watts. I try to only use 80% of the rated capacity of the PSU. I tried to not skimp on anything to do with power and play things safe.
The other thing to look for are the cables that come with the PSU. I have a SilverStone ST-1200-PT and came with 8 PCIe cables (8 pin to 8(6+2) pin). Certain 700watt PSUs only have 2 or 3 8pin PCIe ports on the PSU. So while you might have the wattage you may not have enough ports or cables. Also do not buy aftermarket cables unless specifically for your PSU, the connector going into the GPU is standard but the connector going into the PSU can vary by manufacturer.
For CPUs I use Pentiums just based on availability at the time but would of went with Celeron. My preference is SSDs, got mine for ~$30 for 30-60gb ones. I have a couple test OS builds on USB sticks that I seem to have issues with, but granted these are cheap freebie sticks.