I also think 1080s can be the best option under not-so-special circumstances (price, performance, profit, power cost, power consumption, space saving...). Also if you check whattomine.com calculator page, it will tell you the profit is quite reasonable with this card. To match 3x1080 you would have to buy more expensive 4x1070. Sure, it varies, but in my case 1080 is a better fit, even if I expand to 6 card rig. The 1080ti is out of my financial capabilities though.

So, long story short bought 3x1080 on ebay recently. They were about 20% more expensive than 1070s, and easier to find.

As the rig is still being built I'll probably jam the cards directly on the gigabyte h110 d3a motherboard for the time being. Also waiting for the riser delivery. Cooling is not a problem, it's winter and my cellar is around 5-10°C at all times.