Yes, each of the zones has wiring terminating in a different location (wired circa 2000). There is a media cabinet on the main floor for the speakers on level one, a panel in the master bedroom for the second floor, and a panel in the garage for the garage speakers.
If I understand correctly, this is what I think I want to do. Right now only the main floor has a receiver, and older Denon. I'd like to get a Sonos Connect for it, so I can output iPhone/iPad/iTunes media to it. This location has ethernet, so that unit can be the base of a Sonos network. The only thing I'm unsure about is what I can directly output from my iPhone. The app says I can send "iTunes media" to the Sonos, but if I use a different third party Podcast app, for instance, I'm guessing I'm out of luck, the app will probably only grab media from the standard iTunes folder on the Mac or iPhone/iPad. Therefore I'm tempted to get an Airport Express so I can use Airplay to send whatever output from whatever App I want from my device to the Sonos.
Since the other 2 zones have nothing hooked to them, I'm tempted to get
Sonos Connect:Amp for those. I could then play iTunes directly to them / play different sources from the main floor unit, as I understand it, or play the same output as the main floor Sonos. Therefore the only reason for an Airplay Express on these two, if I understand correctly, would be to play different iPad/iPhone streams (say from my wife's phone) directly to these sources.
If I understand the Airport Express, I could use it with my existing receiver to output my phone to the main floor, but it requires something to drive the speakers in the other zones, correct? The one open item in my mind is the driving several Airport Express units in each zone at the same time. I've not tried that before, in my experience I've only used one Airplay "out" from my phone at a time. Are you saying that AirPlay will allow me to select three Airport Express units at the same time from one iPad or iPhone? If so, that's fabulous, and means I could just pick up really cheap receivers and connect each of them to Airplay Expresses, correct? In that situation would the Sonos' provide me any value?