I would like to create a dedicated area in my home to listen to my digital music library, which resides on a NAS. I currently have SONOS throughout the house, but I would like something different for my listening room. I find the SONOS app is not very user friendly for local music library. I am not interested in any streaming services, just my music library.

I prefer passive speakers with amplification. I tried HEOS and Yamaha MusicCast when they first came out, and was not impressed with the local libray control.

It’s good to have Remote Central back.

I think you have a lot of options, ranked from $ to $$$$:

$ Sonos (I know that's out, but might as well keep around as a comparison)
$ PlexAmp (might be able to run Plex on your NAS & Airplay / casted to a compatible endpoint)
$$$ BlueSound PowerNode (or Node if you have an external amp)
$$$$ Roon (might be able to run Roon on your NAS, with a suitable endpoint)

If you want to really be engaged in your music library the Roon experience is hard to beat, and IMO with the same digital file played back on the same hardware Roon playback was noticeably superior to PlexAmp, with a lower noise floor and more clarity.

HEOS and MusicCast, when they first came out... they have changed significantly to be fair.
MusicCast less so, but HEOS has global search now, you can bring in custom playlists from different services etc + it's SMB 3.0 compatible now.
BluOS / Sonos / HEOS will all do what you want.
However, I agree with others that Roon is the best option out there, but it is costly for what it offers. Plex can deliver a pretty cool experience, but I hate having to keep my software up to date all the time when I just want to plug and play when it comes to music listening (I have a lifetime Plex subscription BTW).

Autonomic?

What kind of NAS do you have? Roon supports their server installation on several NAS, Synology QNAP, ASUSTOR. But they require some hardware minimums that might force a hardware change. You can also run the server on a PC or Mac. Roon Ready players are all over, from entry level to uber expensive and high end.

The one thing that would keep me from using Roon is that they were acquired by Harman, which is owned by Samsung. I am vehemently anti-samsung. I have to bite my tongue when installing those amazing Frame TVs for clients that think they are cool. I feel a little off installing JBL Synthesis product as well. LOL

Aside from that, look into setting up a Mac with the right software and using an iPad or iPhone as the control point. I have been out of the loop on all of this for a few years so I would not even know where to start. But lots of options for improving on the SONOS sound quality. But be prepared to shell out some $$$.

Maybe start with a decent DAC connected to the SONOS and then at least you will have a reference to start the journey of improving upon. I admire your choice to create a dedicated space to enjoy your music though. Something I look forward to one of these days after we pass through the " we can't have nice things" phase...meaning when all the offspring have vacated the premises. :)

I don't have any experience with 3rd party Sonos controller Apps, but some users seem to like them better than the Sonos controller. They are relatively cheap to try. 3rd party controllers can operate, but not configure the system.