Personally I do have Apple Music and Qubuz for music services. I think Apple Music is a good choice for current music and it has also radio stations in which you can skip music. Qubuz has a higher bitrate when streaming directly trough the S2 app. 
When streaming Spotify the max is 320kb. Maybe someone can correct me on this one, but that’s what I remember. 
You mention you don’t care about the HD quality, but the fact you are using Sonos, you probably also want to get the most out of this system. 
 

That’s my personal opinion in this. I’m very curious to other opinions, so I will keep an eye out to this post. It’s an interesting question.

I already had the upgraded Amazon  service for various reasons, so I’m not really impacted by this change. I’d consider switching over for the right reasons, but I don’t see it yet.  I have found that I do like Sonos radio, which you can get for free with ads.  The paid version is much better though since you drop ads, can skip tracks, and higher audio quality.  Same price as Twitter verification.

Just a summary of my curiosity…..

• Spotify: up to 320 kbps, See this article.
• Amazon Music Unlimited: HD (lossless) 16-bit CD-quality and UltraHD (lossless) 24-bit up to 192kHz. See this article.
• Qobuz: 24-bit 48 kHz Hi-Res FLAC, only on S2 compatible hardware. But… Tracks with higher sampling rate than 48 kHz will be delivered to your Sonos hardware as 16-bit 44,1 kHz FLAC (CD lossless quality). See this article.
• Apple Music: 64kbps HE-AAC, 128kbps AAC, 256kbps AAC. See this article. 

I don’t go trough all the services, because there are so many out there. The above 4 are the only ones I considered I would pay for. As mentioned before I did choose Qobuz and Apple Music. 

Qobuz, because I like the idea to get the high quality out of my Sonos system when streaming using the S2 app. That said, I can’t see in the S2 app if the music is available in 24-bit 48 kHz (everything in a higher bitrate will be downgraded, which is a bummer). Therefore I can use the Qobuz app. But when streaming from the Qubus app using Airplay2, the quality will also downgraded to 16-bit, 44,1 kHz. Not to mention, my 48 year-old ears can't even notice the difference between those 2. Maybe I’m just a music nerd, who is psychical about the numbers, LoL
On the other hand, I like Qobuz most of its musical experience. They have very good curated playlists which matches my taste, but that's personal off course. And most important off all.. My wife kind of demanded me to keep Qubuz, since she is al about that streaming service. And I don't want to make her upset by canceling it. She tolerates me to frequently buy Sonos hardware, so we both are kind of satisfied with this situation 🥳.

Apple Music is what I had before diving into the world of Sonos. If you look in the numbers of quality using the S2 app, it’s even more worse than Spotify using the S2 app. But if you own an Apple TV 4K, have it connected to an eARC TV and have an Arc or a Beam (gen2) you are able to get “Spatial audio” which is Atmos Music. Which I believe is a real ‘game changer’ in the experience of music. Although the Amazon Music Unlimited will offer that too, using just the S2 app connected to an Arc or Beam (gen2).

That brings me to my final thought about Sonos Radio HD. Which offers HD radio @ 16-bit 44,1 kHz (same as airplay2). See this article. 
I have tried it free for one month, but eventually cancelled it. It must have been because besides the numbers about bitrates I also might have thought, Keeping Apple Music, Qobuz and Sonos Radio HD in total cost me € 50,- each month. That's for a dual subscription of Qobuz (€19,95), Apple One (€19,95) and Sonos Radio HD (€9,95).
Although the ease for music playing in high quality without worry about thinking about the next playlist, is a breeze to play music in whatever mood you are during the day. Just press play and forget. Not to forget the curated stations from various artists which are only available on Sonos Radio HD and I really did like a lot of those.
I think I will just forget about the €-numbers and give it an another try. Thanks for the insight of this opening post

Long story short… It’s all about what you think is important. Very curious about other suggestions that will come up to this. I am open to everything when it comes to enjoying music.

I would go for Amazon Music Unlimited. Only costs me  £7.99 a month and I can play from the Amazon Music app as well as the Sonos app.

Edit; sorry I forgot. AMU is ruled out because they want you to pay for the service and they are already making profits. Best switch to Apple.

I’ve tried them all and have several Sonos speakers all over my house, yard and garages, including two Connect: AMPs into a hifi McIntosh $30k system and reference theater system. 
 

Tidal Hifi Plus is the king and it’s not even close. Better app and user experience with true lossless audio and master tracks. It’s $20 bucks a month and blows everything else away. Old adage… you get what you pay for. Depends on your needs. If you need something to stream on your phone. Get frickin’ Pandora or some other cheap service. Spotify still hasn’t figured out lossless audio (‍♂️) although Apple is showing up strong with 100M tracks (a lot are lossless) compared to Tidal’s 80M. I’ll go with Jay-Z, he’s got the stuff. Just my opinion. 🫡