I built mine around an N150 board off of aliexpress. 6 SATA slots, 4x2.5G ethernet, 2x m.2 slots. Find a cheap second-hand case, a bit of RAM and you're ready to go. It's got hardware transcoding, handles 4K without breaking a sweat. And it consumes 6W!
The kindle hardware is excellent, but the kindle software is one of the worst pieces of garbage ever. Just filled from top to bottom with utterly deranged behaviors.
https://slatestarcodex.com/2017/05/26/the-atomic-bomb-consid...