OK, say I go for an S10, I presume I still need to access the music files on the NAS via a smartphone/tablet/computer by Plex or similar. Whereas full blown streamers from Naim, NAD and Arcam have their own control system?
The S10 has its own dedicated control app.
The make of its internal DAC seems to be a mystery - but it makes a sound that people like and that's what matters.
At the price it must be worth a try (I reckon they'd sell quite a few more if it had digital out).
A streamer I've liked the look of since V1 came out in 2015, is the Cambridge CXN, now in V2 form - far from inexpensive, but not as ridiculously priced as some streamers are.
Another option, albeit without its own screen, is the popular Bluesound Node.
And how about the NAD M33 I mentioned earlier? - but maybe you're happy with the amp you've got - so just need their M10.
Like I said, no shortage of choices for you, ranging from bargain to stupid prices.
I currently use Raspberry Pi / Khadas Toneboard, controlled by Volumio - not much to look at but excellent sound / value.....and small enough to hide away if you don't wanna look at it (or you're snobby about what others think).