I googled for a long time regarding this myself, and didn't find the specific info I was after so I decided to go for it, and now I can post the results.

Living room approx: 37m2 and is an open L shape into a kitchen and dining space. The main listening area is approx 16m2, with one side opening into the kitchen/dining space.

I had a complete HT (Dolby Multichannel 5.0) setup consisting of

-L: Dali Oberon 7

-C: Dali Oberon Vokal

-R: Dali Oberon 7

-SL: Dali Alteco C1

-SR: Dali Alteco C1

-Sub: None (The quad 7” drivers of the Oberon 7s provided plenty for my listening space)

-AVR: Marantz NR1510 (Audyssey tuning used for the setup)

-Media: Mac Mini M1

-TV: Samsung 65” 4K

Now I had some Sonos One SLs in other rooms of my place, and the AVR had AirPlay 2 support, so I almost had a seamless system via AirPlay 2 for my place.

With this setup I had sound in all rooms, excellent sound quality during music while in my living room with the Dali setup, and a very good 5 channel home theatre setup for movies. It did however take up a fair amount of space, cables and well no app support for seamless integration the same way a complete Sonos system does (well of course). So I decided to let go of my Dali setup and expand my Sonos instead.

-LCR: Sonos ARC (placed on top of a media table together with the TV, flat roof for Atmos)

-SL: Sonos One SL (placed next to couch on Flexson floor stands)

-SR: Sonos One SL (placed next to couch on Flexson floor stands)

-Sub: Sonos Gen 3 x 2 (placed next to the media table in a corner and diagonally next to the couch)

TruePlay enabled on all.

-Same TV and Mac mini as previously (still haven’t got the Mac mini to output multichannel audio with this setup unfortunately, it worked flawlessly with the AVR) Have been using a USB drive direct into the TV for my content from my media server in the mean time. 

Experiences:

-The Sonos system in my living room now “of course” integrates very well with the rest of my place, I can walk around from room to room with the same music, and therefore play at a lower volume since I don’t have to have the living room projecting to the entire place (to be expected, but now confirmed for me) I also use Sonos radio and other streaming services in the Sonos App regularly, so its nice that now all speakers in my house can play the same content, use alarms etc.

-My previous setup was only a 5.0 system, and this new system is a 5.1.2, so ATMOS was a new thing for me. I can’t say I feel the overhead effects too well, but yeah definitely nice to have, especially as more and more content is encoded this way.

-I regained a bit of living space, and probably some style point as well, as this setup is very sleek

-HT experience: I would rate it at equal to my previous setup. Slightly down on spatial separation of-course, but up on Atmos and deep bass performance

-Music: Here I would say is the weakest point for me. Listening to music via my Dali Oberon 7s, they were able to reproduce a depth, especially on the lower frequencies that was just a lot more dynamic and controlled at lower volumes (don’t really listen at very high volumes often, had my AVR up to -17db and my Sonos from 15 to 50-60% volume) This is also not using some super high fidelity recordings, but anything from 128-320kbps tracks mostly.

Since music wasn’t really where I wanted it, I decided to swap a ONE SL I had in the kitchen (which projects into the same space as the ARC setup) with a FIVE and use in together with the ARC setup when playing music (just grouping them). This did help with spatial separation and clarity but I would say maybe a 10% improvement, so not a whole lot, but keeping it as it also freed up a ONE SL to place elsewhere in my house.

Next was to try dual sub setup, sound is a lot of physics and replacing quad 7” drivers with a soundbar and a single sub, yeah well something had to give. Maybe a second sub could help with my music desires. Got the second sub and I must say it did improve the situation, I think I will rate it at about 90% of my previous setup now, and even with the sub being expensive, I will keep both, as I want to be as close as I can to my previous Dali Oberons. 

Conclusion: I knew I would be sacrificing some “fidelity” when going from floor standers and an complete AVR setup to a Sonos, but had hoped the music would be closer in comparison, now I am not going to switch back at this time, but if music is really important then keep your floor standing speakers. But I gained ATMOS, ease of use, space, design and other than a slight downgrade music wise it performed just as good or better in every other arena.

Wishlist for SONOS:

-ONE SL that are Atmos capable, so I can have rear channels with Atmos as well

-Be able to use FIVEs or ONE SL as dedicated left and right channels for HT and the ARC as a dedicated center and Atmos channel

-Siri integration, I prefer SIRI to the others, due to privacy.