I use SONOS zone (wireless) out by my pool, which is similar to Squeezebox.
I have a JBL marine radio head with the Sonos plugged into it's AUX port. That allows us to play the same lineup that you have; iTunes libraries and playlists, NAS files, Pandora/Rhapsody, etc. The marine head (JBL) is also Sirius capable. We control it with either a SONOS remote, or with a smartphone with the SONOS app. It allows us to control not just music selection, but also volume, balance, etc.
I power the marine head with a MeanWell S-150-12 inverter, it was $35.
The JBL head drives four Yamaha speakers. I forget the model, but browsing online my speakers look exactly like the current NS-AW570 speaker.
My system has been in for 8 years, maybe nine. It's survived the New England winters. No component failures.