Maximus VIII Hero here, with I7-6700K OC'd to 4.7GHz running a Corsair H80iV2. My voltages are similar to yours, and I see similar temps on the cores. Gaming tends to run 50-60C, occasionally hitting 70C when running MS Flight Simulator at extremely high detail levels. Stress testing with RealBench hits around 75C, and benchmarking and heavy Handbrake encoding can drive it to 80C on my hottest core occasionally. That's with a smaller but efficient AIO cooler, so it's pretty typical. The push-pull fans on the radiator draw outside air into the case, and a 200mm fan above the CPU and memory area pulls the warm air out. The case has a push-pull fan arrangement through an empty drive bay that blows air into the CPU area and across the video card, and another single intake below that blows across the hard drives and below the video card towards the PSU. Plenty of airflow works well even with a relatively smaller cooler.
Motherboard: Maximus VIII Hero
Processor: I7 6700K - 4.9GHz OC
CPU Cooler: Corsair H80i v2
Memory: G.Skill DDR4-3000 16GB
Graphics: EVGA GTX 1080 FTW2 1721/1860MHz
Storage #1: 1TB Western Digital Black
Storage #2: 2TB Western Digital Black
Case: Antec Nine Hundred
Power Supply: Antec Edge 650 80+ Gold
OS: Windows 10 Pro