I’ve had several conversation with people I consider veterans in mining about rigs to build and as of May 2017 this is probably one of the best ways to go. This CAN change at any minute with new cards, software changes and etc. So if you’re reading this more than 30 days after this is posted, consider it outdated information!
My thoughts on this:
Mobo - the TB250 - BTC by Biostar
6x 1070 318.99 € newegg uk (each) (you can two for below the power needs of a single 1080ti and get more H/s)
If you are worried about heat!
6x 1070 water cooled newegg uk is $349.99 € each (unsure of power but less heat 1080ti and more H/s for less money)
cpu, just make sure it fits the socket of Mobo suggested, but its fine
Ram - fine
ssd - fine (don’t forget o/s)
PSU and this is just a sugesstion [Hercules 1600w gold std power supply]
(Rosewill 1600W Modular Gaming Power Supply, Continuous @ 50 Degree C, 80 PLUS GOLD Certified, SLI & CrossFire Ready - HERCULES-1600S - Newegg.com) @256.99 €
6x - 1080ti = roughly 4,500 H/s at a cost of (cards only) $4,488 €
6x - 1070 (air cooled) = 2,700 H/s at a cost of (cards only) 1,914 €
6x - 1070 (watercooled- LESS HEAT) = 2760 H/s at a cost of (cards only) 2,100 €
In case this needs even more explaining:
You can build x2 1070 air cooled COMPLETE rigs, for less than a single 1080ti and have on average 700 more H/s
You can build x2 1070 water cooled systems for around the same price as a single 1080ti system with more H/s