It is a pitty that Qnap does not support ryzen gen2 in their systesm.
But if I look at the x77 and x82 series, then I really wonder what I should do with the 2.5" bays.
SSD is simply to expensive,, and with what I think I will need is a maximum of 4-6TB.
I have the 673 and it is a nice device. Got a new from Qnap as the previous one had issues with the backplate. So that model does not "feel" right. Maybe it was my fault, because I put a lot of 250gb disks in it in the beginning and upgraded to bigger when needed. (had a bunch of notebook disks, and it worked...)And that changing disks is not good for the backplate. But if I listen to others, then they use that system form backups. Put everyday a new disk in it, and they have after 3 years never an issue, I have an issue after 4 times. That on a sidenote.
I am satisfied with the 673, just falls a bit short. Something heavier would do good. The 673 with 4* 2.5" WD red consumes 50-60 watts, which is about equal to what the 877 or 872 would consume.
I might wait a bit longer and see if Ryzen gen 2 comes in a desktop version. Or the 8700t will be available and I might buy it, in case I buy the 872 and hold it back until the guarantee is gone. But like you say, there goes nothing beyond the Ryzens yet. But this 2.5 is something I never use, but you pay for it, like Thunderbold 3. I do not use it, but pay for it.
Your suggestion is build a ryzen pc and use that one for Plex-servings, is something I have been thinking about to.
But with electricity prices going 30 ct per kilowatt, over here, it is not something I am wanting to have.