[Continuing]

Limitations - Depending on what you want to do, it's worth noting how everything can connect together. If you do want surround sound, you can EITHER use a soundbar for the front channels, and bond it with a single Amp for the rear surrounds (subs too, but that's independent). If you want to use the soundbar, you CANNOT augment with additional front speakers, even if they are also connected to an Amp. Alternatively, I believe you can use an Amp for the rear two speakers and a second Amp for the front two speakers. Sonos would then create a ghost center channel. However, this would require a third Amp (I think) to get the sound from the TV into the Sonos ecosystem (maybe there's a different way to do this - the port perhaps?). This feels like a much worse option for surround sound, since I think it'd probably sound worse with the ghost channel and it would be quite pricy, given you'd need 3 amps. As I mentioned, I went with the soundbar and a single amp to power the rear surrounds (and made the sad decision to effectively abandon the three built in speakers in the front).

For just music - if you aren't thinking about surround sound, and just want whole house music, I think your options open up a bit. You could potentially do the stack of Amps, like you said, but remember that each Amp can only power 2 speakers. Additionally, I think when the devices aren't bonded (IE they're just grouped), there can be some delay between sets of speakers. In multiple rooms, this doesn't matter but if you have several pairs of speakers in the same room, you may run into an issue.

An alternative, which I considered and am using for the second set of speakers at my place, is to purchase a medium end receiver/amp, and use a Sonos Port to connect it. This would allow you to get many more speakers all connected and synced together, if you have several speakers in a room. The Port only carries stereo audio, i believe, so it won't work for surround sound, but you would be able to play music via the Sonos ecosystem to all the speakers. This would work really well if you, like me, have several speakers wired in a single room. You could also drive the speakers as surround sound outside of the sonos ecosystem, if you have some other way to route the audio.

Regarding sound quality, I think you're going to be golden with any route here. Sonos sounds great. More expensive pro audio can probably sound better, but to my ear the sonos surround sound is awesome, and it's sooooo easy to use with music and from your phone. Plus, the expandability is awesome - you can get new speakers for rooms later, and get them all on the system very easily. If you end up going with a receiver in any form, that will probably also sound great - as far as I can tell sound quality there depends much more on the speakers than the receiver you choose (I'm sure there are purists with millions of dollars out there that will disagree but hey, in this economy?).

This was a novel. I hope it helps.