I'm by no means an "expert" (first post here...) but I'm very happy with my Hardkernel HC1 on Armbian, which runs 100% stable as a NAS / Video & Music (Slimserver) server system. That said, worth thinking a bit about the disk(s) you plan to use. If you want 3.5" (desktop) spinning disk(s) - arguably more robust, cheaper $/TB, higher capacities available, then you'll need 12V Power, so an HC2 would be a better choice for an established CPU from a board vendor who seems pretty good and proactive to me. If I was starting again and wanted something a bit more "serious", then a Helios 4, a 2nd-user HP Microserver or maybe the new Pine64 RockPro64 with Dual-SATA NAS enclosure - https://www.cnx-software.com/2018/07/13/rockpro64-dual-sata-nas-enclosure/ (worth looking at the comments belows the story) seem like the options I would look at now, although as per comment above the RK3399 / RockPro64 may need some time for the software to fully stabilise.
Definitely worth thinking about the "physical" side of things if you want stability - heatsink / cooling, power, enclosure, fan or fanless. I like the HC1/HC2 because of the decent heatsink, proper connectors and power setup, but if you want multiple disks (or the ability to expand in future) then one of the other options might be worth getting. And (obviously) figure out what your backup regime will be!
