Plays all games at 1080p with no issues, most will play at Ultra/High, some like Witcher 3 at Medium. We had a blast with these little rigs at the Fites LAN 2019, ask any serverbuilds moderator or especially @voltaic (he has the same rig) for more info.
Build is based on this video, with quite a few more odds and ends, upgrades, and accessories.
Intel Xeon X3470 quad core with HT (3.6GHz turbo)
12GB DDR3 ECC
EVGA GTX 1060 3GB (new)
128GB Silicon Power SATA3 SSD (new)
2TB WD RE4 HDD
Asus Xonar DG sound card
USB 3.0 card + USB 3.0 front ports (add your own, pre-wired)
USB AC-Wifi adapter
850W Rosewill Hive Modular PSU (basically brand new)
Arctic Freezer 12 CPU cooler
Cooler Master Q300L M-ATX case (basically brand new)
$300.00 + shipping OBO, or local pickup