Ok, I read the initial post more carefully again. The first thing I don't understand is why you want to use a Sonos Amp with Sonos One as a front setup. The Ones are active speakers, aren't they? So if Sonos as a streaming multiroom solution is important to you, I would rather go for a classic home cinema system with AVR and Sonos Port in the living area. Then use the already existing Play 1 in the adjacent rooms and on the terrace, the subwoofer as support in the most important adjacent room, and sell the Amp. If you still want to use the Amp in connection with classic stereo speakers and continue to use it, I would also set up the home cinema based on these stereo speakers (with Port and AVR). In the approach you have in mind, you will always only get 4.0 multichannel stereo with subwoofer support. That is not a real home cinema.