You'll need a NAS of some sort to stream the music to the Sonos if you want to avoid keeping the Mac on.
I bought a Play 5 and think it is an awesome bit of kit, want to get a Connect next to plug into my amp in the living room
Yeah it's awesome,one in living room and one in bedroom connected to mine and the girlfriends iPhones and my ipad,set up was a breeze but there are a few things I need to find out about it as its all new.
When I added my iTunes library when going through the install procedure it was a breeze,but when adding more albums to iTunes I don't seem to find away of updating the sonos program on the iMac,I can use the phones and ipad to update music lists and that works but the IMac music list on the sonos remains the same.
I have seen a time when you can set it to update media,but.not found a quick way of doing it as soon as I have added other music