OP update: I finally got one. 
NUC8i3, 8GB RAM, 256GB Samsung EVO. 2TB Crucial MX500 SSD for library storage. So far running well, though it’s not as snappy as Roon Core running on my 2017 iMac i5 (started a separate thread for that). I switched the NUC cooling to quiet mode in BIOS and so far the fan only runs at a very low speed during playback, and shuts off at idle. (Caveat: it’s winter and cold here.)
Processing speed seems adequate for single zone with very light DSP use - I do think you should get an i7 if you want to do anything more than that. I’m debating if I should have done that to have a bit more headroom and snappier navigation, but I’m liking how quiet the i3 is - the fan is unobtrusive at low speeds.
Here’s a snapshot playing a DSD file, 4x processing speed. With a 24/96 file it’ll be more like 70x, so it’s really just DSD that taxes it.
