No hands-on experience here with either Star or Sonos.. so caveats all around, but..
1. My Atom, with server setting 'on', is browsable on my TV as a DLNA server, and on my VLC clients (on iPhone and MAC OSX) as a uPnP server. It shows folders for Album,Artist,Genres,Composers,Conductors. (I'll load some music on a USB key and verify It works, tomorrow.) Also, the Atom shows up even when in standby. Would need to confirm Sonos browses similarly. Sonos support site implies uPnP should be ok.
1.b. I think you'd want to use the Sonos app as the control point for multiroom control, if you're already vested in Sonos. I chatted with Sonos support and they said Sonos connect line out to Naim line in would work, syncing your rooms. But you'll still need to flip the Naim to line-in, so two apps. My Atom gives ability to set line-in with "slave" volume control, so presumably you could control volume from Sonos app.
If you're stuck on the Star CD player..
2. Not sure if you can rip from Star to NAS directly. Need someone with experience to comment. I know that I don't see a way to mount a network drive from my Atom, I can only browse as in (1.), or mount a drive via USB.
3. If you can't rip to NAS, then you'll need a USB drive. If that is the case, then you'll likely just serve directly from the Naim and forego the NAS.
4. You'll still need a NAS if you intend to backup. If the backup isn't encrypted, then it 'might' be possible to serve it with a NAS media server app/add-on.. but that would be redundant if (3. using Naim as server). Need confirmation on the readability.
5. There are some newfangled simultaneous USB access NASs now out (browse for "Quick Access Port" on the QNAP site), which may allow the best of both worlds. Theoretically, you could rip to NAS via it's usb, then network serve from either Naim or the NAS, and have RAID drive redundancy. Lots there to verify though.. like what if the media server app doesn't serve the USB mount point due to a restriction?.. bleeding edge.
If you're not stuck on the Star CD player..
6. Just rip everything with a laptop and loaded it to a NAS. I think that allows more flexibility (formats, tools, control).
My enlightenment..I use Tidal to stay current, and my rarer stuff is ripped and sold. I personally don't see the need for a CD player anymore, after spending the summer moving to NAS.
I'll also bet my semi-distant-future will be NAS-less and service-full. I believe I've hit an inflection point where the content services are better than what I can build and maintain. So in the end I'll just have a streamer, an amp and speakers.
Sorry it took a while to type this, you may already have your answers by the time I refresh my browser LOL.