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?