FreeNAS, unRaid they all recommend ECC. Do you actually need it? Probably not, from my experience.
I've been running my FreeNAS box with non-ECC for the last 5 years with 3 reboots. Never had any issues or missing data.
If you get something like a qnap you'll be locked into whatever cpu / memory those things have.
I run FreeNAS for storage and Emby on my media server which is hooked to some Rokus.
My media server has an fx-8350 (upgrading), 16GB memory and a 1070. Once you start trans-coding stuff higher then 1080 you'll want a better cpu. Keep that in mind.
I'd recommend building your own NAS if you plan to use it for a media server / trans-coding. You'll have the option to upgrade down the line.
I've used Crashplan for a little bit to send files from my PC to a computer at another location. It was free, worked alright. It was free.
My advice would have a VPN between the locations and use RSYNC to send the files from / to a share on each side. You could even use something like SyncToy that sends data Left to Right.
This. Quick and easy to do. I bet you could even go to your local craft store and find a Sharpie that matches the current paint. That would save you the hassle of painting the whole thing again.