I started in the kitchen (large room) with the Play:5 (it will easily provide enough sound for a large room) and it is about $500 so it isn't cheap. The sound quality is unreal though. If that is where you spend a lot of your time, I would recommend that route. You might be able to get away with a Play:3 to save a little money but they don't put out nearly as much sound.

On my porch I paired two Play:3 speakers - if you spend a lot of time on a porch that could also be a good place to start. If you are a movie buff, you could start in a theatre room but that would be the most expensive place to start. You could get a Soundbar, Subwoofer and two Play:1's as the surround speakers. The sound is incredible and you can also play music in the room via the app.

The best two things about Sonos are the sound quality and the app. Via the app you can add any and all of your existing music services (Apple Music, Amazon, Pandora, etc) and play pretty much any music ever produced. You can also play different music on every speaker and/or combine them in any way.