In my case (Antech P182-SE) I have:
Asus X99 Deluxe (BIOS flashed properly to support my CPU)
4x 8GB Hynix ECC DDR4 server RAM in QUAD ch
Xeon E5 2630-v4 ES
AMD R7 series GPU (unraid GPU - no integrated graphics on CPU)
Nvidia 1060 3GB (for Winblows 10 VM - Gaming/CAD/CFD/General)
PCIe 4x USB 3.0 hub (VM passthrough)
Corsair GS700 - works fine.
Cache drive - Samsung 960 EVO M.2 (want to double this up but might swap to 2x cheapo 512GB Sata SSD's - M.2 is literally 4x faster tho!)
Boot drive - 2GB Geek Squad USB 2.0 Flash drive (backed up to the array)
Array 6TB:
Parity - HGST 3TB 7200RPM refurbed Sata 3 (might upgrade to 2nd parity for redundancy)
Drive 1 - Seagate Pipeline 2TB 7200RPM Sata 3
Drive 2 - HGST 3TB 7200RPM refurbed Sata 3
Drive 3 - Seagate Barracuda 7200RPM Sata 3
In terms of gaming with GPU/CPU pass-through: Doesn't make a noticable difference. Can run Modern Warefare 1080p at 200+FPS. Arma 3 in 4K at 30-60FPS (playable), Asseto Corsa 4k @ 60FPS (with some setting dialed back), High scores in Benckmarks (1080p) and cinebench (thanks to 8 Hyperthreaded cores pass-through).
CAD/Video Editing - The main reason for this build along with the NAS redundancy. Can run Adobe Premiere Pro CC without issues or stutters, transcodes 4K DJI/Gopro footage without a sweat in minutes. Can compute CFD(Computational Fluid Dynamics - think virtual wind tunnel) without much trouble in under an hr.
Other thoughts: Swapping the 1060 to a 1080ti when the price is right. Even though a 1070 could max out my 2.1GHz CPU, the 1080ti would technically transcode faster and with the extra CUDA, could complete CFD runs faster. I seriously can't tell the difference of windows being a VM on unRaid vs bare HW.
If your intending to build a multi-gamer/NAS box here are a few suggestions:
Fairly newer Xeon 2-6 CORES (not threads) per gamer
DDR4 (or better) quad channel (ECC recommended) 8GB MIN per gamer
Depends on the Xeon you choose, 2-3GHz and large L2/L3 cache can support up to 3x 1070's a Xeon of 3+GHz will support 3x 1080ti's (all in full PCIe 3.0 x16 mode)
For 3x Win 10 VM's look for mobo that has lots USB native, dual M.2, and 3x PCIe 3.0 x16 slots
2x M.2 drives for the Cache/VM homes (this will keep the OS snappy). Can set up unRaid to use 2x M.2's as cache drives, they will be mirrored for redundancy. (something I should have done with my 7yr old SSD cache drive, RIP recent Windows 10 VM)
At least 3x Sata drives for your Parity/Array (These can be as little as you like, but parity must be => any one array drive).
PSU to support 125-150% of the HW you plan on stuffing into this monster!