I'd say that most people have been interested in the ASUS 970, but my actual customers have used a fairly wide spread of brands. The Gigabyte one has the most users. I'm trying to rotate out and try them all myself for my full build customers.
Here is the build I am doing this week--the motherboard and SSD work great together and I am sticking with it as I know it works well for the S4.
Cooler - NHl9i
Samsung 950 PRO -Series 512GB
Asus GTX 970 Mini DCU
HyperX FURY DDR4 2666
Motherboard - GA Z170N - Wifi
Windows 10 (64) Home Premium
Premium bulgin switch & wiring
S4 Mini (LE Powder)
NFC-Systems PCIe 16x Ribbon
HDPLEX HiFi 250W
Dell 330w or Voodoo 350w
CPU i7 6700 (65w TDP)
I like how the Asus 970 has a backplate and uses a vapor chambor for its heat plate. I'm not sure about the omni-directional cooler...It doesn't seem ideal in the S4 Mini at that high of a TDP. It might work out fantastic--I dunno, which is why I am trying it.
I noticed how you have a Voodoo 350w I am new here and interested in building in one of the S4 cases. Do you know where I can buy the Voodoo 350w in the US. Also I plan on throwing a 6700 non k with a R9 nano is the HDPLEX enough to handle it?