I am a little confused by your question. Are you trying to have all your music stored on a NAS device and have those music played by iTunes running on a Mac? If so, your Mac must be power on in order to run iTunes.
If you are going to use SONOS connected to a NAS directly or through wireless then you don't need to turn on your computer and you will not be running iTunes.
Setting up a NAS for SONOS should be simpler than setting up NAS for iTunes on a Mac.
I haven't read your earlier posts, what is the main reason you want to use a NAS device instead of USB external drives?
If you are going to use SONOS connected to a NAS directly or through wireless then you don't need to turn on your computer and you will not be running iTunes.
Setting up a NAS for SONOS should be simpler than setting up NAS for iTunes on a Mac.
I haven't read your earlier posts, what is the main reason you want to use a NAS device instead of USB external drives?