Boots FreeNAS (2xZFS mirror) off a little Sandisk usb drive, it's a pretty quick box and uses 19W at idle, up to 45W at full tilt. It's impressively responsive for something that's attached via gigabit ethernet. I moved the rear fan to the front for better HDD cooling (2x fans in the front now).
I wanted a G4560 but stupid bitcoin miners made them unavailable. Had to scratch and claw to get this crappy Celeron, actually. But that's OK, my RX480 is making $5 a day to make up for it :D
Used the H170 Pro4 because of the 6xSATA ports and Intel LAN. Bought a cheap B150 bazooka to replace it in the build I pilfered from. Oh, and the audio is excellent, too bad I won't be able to use it anymore.
RAM is actually Crucial ValueRAM. Not listed for some reason.
The PSU is mounted on an adapter plate to fill in the gaps. It mounts fine without it though, I was being a perfectionist. Cables are too short though, so I had to use a SATA extension.
With weekly scrubs, all my cat videos are safe from data corruption now (well, compared to Windows, at least).
**Updated Sep 2017: Added a 10Gb Intel X520 network adapter with a direct copper connection to my desktop. While Windows networking is hugely inefficient, I can still get 450MB/s sustained which is good enough for me! Can occasionally hit 700 but it takes over a full 6600K core and my desktop gets quite stuttery/laggy.
Idle wattage now 25W. Pretty happy with the result and the minimal fuss.**
Cheap but the G4560 is better value. Was only budget processor available at the time.
Lovely little board. Very efficient and full featured with Intel LAN.
They seem solid and well priced. No faster than the Desktop HDD/Barracudas.
Nice case, the rubber grommets do slide out too easily and a screw-free fan filter system would make it perfect. Quiet, robust and full of room for activities (and 3.5" drives)
Well made and the cables are not too stiff. Quite short though, so I probably should have bought a full ATX PSU.