I was thinking of getting a few 1070s to start. Here are my options based on stock:
(3) Gigabyte Overclocked 8gb at $390/each
(3) Gigabyte G1 8gb at $410/each
Should work well together, IIRC they are set by Gigabyte to almost identical factory overclock.
I suspect that first one you listed is the one I have 6 of.
For a triple 1070 rig, I find a good 850 watt PS is more than enough - could probably get by with a 750, or a 650 with enough undervolt and core downclock.
I don't build riser rigs, and my rigs don't tend to be pure "mining" rigs though.
Most of them are built on the ASRock FM2A88X Extreme 6+ (using 2 full-length 1070 and a Gigabyte "ITX" short 1070).
Same motherboard could work with a pair of 1080 or 1080ti in the first 2 slots, but keep the "shortie" card for the third slot for cooling - and you will definitely want more PS for a pair of 1080ti (power draw on the 1080 is normally 20 watts or so more than the 1070, not exactly a big difference).
For a pure mining rig, I'd probably go ASRock 970 Extreme4 (my current gaming rig and one other rig are built on this MB).
Pretty much any "3 x PCI-E 16-bit slot" board should work, as they all have the same 2-5-7 spacing as the pair I mentioned, or the Gigabyte board Phil mentioned.
