1. How many gpu per mb are you planning? EVGA's largest psu's will limit you... i would suggest server psu's if your serious. I run a single 2400w with 7 nvidia + 2 amd on win 10 without it breaking a sweat. No dual psu crap, but requires 240v power. If you are serious run your atx at 240v. Better efficiencies no matter the brand.
2. 570 & 580 in that order. Stupid deals lately...570 4gb for $199 usd after rebate. 4gb is a short sighted purchase but I don't usually mine eth. I just bought 4 more to max out my rig...check newegg.Com
3. #1 dictates your mb. I am on h110 pro btc+ and rock solid out of the box.
4. IMHO Vegas are power hungry but are getting better with recent mods...but $$$
My setup...
H110 pro btc+, I run 8gb memory, m.2 ssd and decent celeron cpu. I use a 250w pico psu and a 10 port Pwm fan controller. All cables are pcie 6 pin from server breakout to all devices, no molex or sata shit. Risers are v008s with 6 pin pcie power. 7 x 1070ftw, (4 x rx570 on the way), 1 x rx470, 1 x rx480. All on spotswood extruded aluminum frame. Total cost about $3800 by adding up in my head. Mostly used stuff from eBay and newegg fire sales.
My advice...
Get 8gb memory for mb... run a m.2 for faster virtual memory, i run a 30Gb swap file and the m.2 does help...get something better than G3950 cpu...buy new cards, used is more than new...buy good cards with no less than 2 yr warranty. Rx480 is great, rx580 is less efficient, rx570 offers good performance with less power and price. I will not buy a 580 and my 480 reference card lays down some good numbers but fools on ebay are paying $250+ for a 480 when you can buy a 570/580 for $200/220 new? Wtf?
Quoted post is great advice. Thats exactly how I would build more rigs myself. However, i'd opine that RX VEGAs are extremely efficient and profitable right now mining electroneum/monero and with the power play registry edits (1950+ H/s on 130watts). But if you want to strictly stick to ETH then the cards mentioned are fine.
Just one question, when you say:
If you are serious run your atx at 240v. Better efficiencies no matter the brand.
Do you mean better power efficiency? If so, how do you configure PSUs to run at 240v? At stock they run at 220v right?
Would love to know more.