Are those GTX 1080 really that bad? Because price-wise I can buy 1070 for $520, 1080 for $575 and 1080Ti for $825.
take Asus Strix 1080ti or EVGA Hybrid
those cards are the BEASTS -they are cold and can easily be overclocked to run about 2000Mh @85-90PL
and, most important, they are delivering almost TWICE performance of single 1070, but with LESS cost then two 1070
let's take your prices, for example, two 1070 will cost you about $1040, while one 1080ti with almost same performance as two 1070 will cost $825.
now you see which one is better, and one more thing if you choose to build 6-7pcs of cards, you will save on CPU, RAM, SSD, mainboard and so on in case if you go for 1080 ti, cause for the same performance of 6x 1080 you'll need two times more ram, cpus, ssd and so on, cause it would be 2 rigs instead of one.
so I'm voting for 1080ti
