I actually built this almost 5 years ago and started making one of these posts right after, but never got around to finish it so I figured its due. Built it mostly for storage but it has also taught me the joy of Docker. Main usage has been as a media server.
Mobo: Supermicro X8SIL-F
CPU: Intel® Xeon® CPU X3470
Cooler: Hyper 212 Evo
RAM: 16GB (4x4GB) DDR3 ECC Registered
HDD: 3x8TB (shucked WD Elements)
Chassi: Node 804
Fans: Assortment of different Noctua-fans
PSU: EVGA 700B 700W (not modular, which Ive regretted since)
Spent more than expected on everything, but it has served me well. Only real issues was the first motherboard I bought had some bent pins, but I got a refund and bought another one (the one with the bent pins I think was an X8SIL, but for the second one I went for an X8SIL-F). Also one of the disks failed within the first year, but I managed to un-shuck it without damaging the plastic container and got a new one through warranty… 
I havent really done a lot with it physically since I built it, but since the disks have been running 24/7 for almost 5 years (over 40000 Power on-hours as of writing this) I’m currently preparing to buy some new disks.
Some of the first parts I got. I started with just 2x4GB, but added another 2x4GB later on.
Bent/crushed pins:
Booting it up for the first time:
Disks arriving from Germany:
Web interface as of today (upgraded from 6.9.2 to 7.0 just yesterday):
