I've always been confused about what Sonos does (probably because of poor communication from the marketing depart). I would love a wireless 7.1 sound system for my TV in my media room, but I always got the impression all Sonos was good for was distributing sound throughout your house (which I have zero interest in).
It sound from your post like Sonos speakers can be used the way i want, even though after spending way too much time looking on their site for that info it didn't seem like it was possible.
Look elsewhere. While you can probably set up Sonos equipment to get close to what you seek, you can do much better in ONE room with a good receiver and 7.1 speakers especially for that objective.
Sonos is really about whole home audio- mostly stereo- readily pumped & playable in any and all rooms. They have several options for making that work but the big point is being able to have some pretty-good (sounding) speakers playing (mostly music) audio anywhere in your home... or EVERYWHERE in your home. If the rooms are wired or not, wired network or wifi, they have all such bases covered well.
If you've been in some big store and roamed about section-to-section and heard the same music everywhere you go, that is somewhat THIS but at your house. Or maybe you want some songs from iTunes playing in a couple of rooms, Junior or Juniette wants other songs from iTunes playing in his/her/their rooms, etc, Sonos makes all that pretty easy and it sounds very good. Yes, it's possible to approximate the same with other products and various setups involving airplay, etc. but Sonos is pretty much "just works" simple, sounds good, and is arguably easier & more refined than many copycat options.
Having a party and want to play the same music all throughout your home? Sonos will do that well- even syncing it all up well so that there's not a little delay from room to room.
One of the biggest deals about Sonos vs. many other options is it's wireless reliance on wifi instead of Bluetooth. Much of what you've read about Bluetooth audio is true, especially the glaring weakness that comes from it's relatively limited audio bandwidth. Streaming audio via wifi doesn't hinder quality in that way. Head-to-head with the same speaker, it will SOUND better.
What you want is something different. You want super sound in ONE room. Sonos has some options to go in that direction but you'll get more for your money buying a receiver and dedicated speakers for your application. If you want to jack in that setup into an overall Sonos setup, you can buy a little box from Sonos to pump audio out and into the receiver so that your 7.1 speakers join into the chorus (of whole house speakers).
I hope that helps. Some of us will bash Sonos because it's not Apple but- IMO- Sonos is the most Apple-like player for this kind of thing going... including how they price their stuff.
Yes, there are other ways to accomplish the same kinds of objectives but that could be said for products competing with Macs, iPhones, iPads, etc too. Sonos "just works" and "just works well" with iTunes. When iDevices leave the home with their owners, a Sonos system can still work just as fully and completely as ever.
