I'm running a Gigabyte Z170N-Gaming 5 Mini-ITX with an i5-6400 on the F4d BIOS (last version that allows BCLK OC).
i5-6400 @ 4.05GHz
BCLK @ 150
CPU vCore @ 1.20
Stock Cooler w/ 120MM fan right above it (Silverstone Raven Mini-ITX case).
OCCT TMPIN2 is around 63-67C
Gaming (Rise of the Tomb Raider, Elite: Dangerous ...) 58-62C
CPU-Z Validation:
http://valid.x86.fr/mrmgzj
FRAPS shows about 30FPS @ Stock, and 41FPS @ 4.05GHz while docked in Elite. I'm pushing a lot of pixels surround monitor setup on 1070.
I suppose the big thing here is why not save money on the MB, get a mid-to-low end Z170 on sale and shoot for a 6600K. Motherboards are where we all drop too much money on fancy-shiny-neat features we just do not need. At least that's my opinion. At the time I picked up my MB for $120.00 sale. Though I see Z170 boards dip below $100.00 often.
I only went this route because I was able to pick up a i5-6400 @ $120.00 8 months ago and kind of lucked into the BCLK overclock thing.