New system design

Hi. So i'm looking to install sonos to my new house and wanted to check about a few things:
To save money i'd like to buy 1 Conect:Amp to serve my master bedroom and en suite. This will involve me connecting a pair of speakers in the bedroom and a stereo speaker in the en suite direct to the Amp. I understand I will need to match the impedance (using blucube BLU-CCL-650). However, can I somehow use something to control/ switch the volume of the en suite speaker? I have seen a QED speaker switch, but ideally wanted a wall mounted item?

Another thing is that I have a nice Arcam set up in the lounge with some B&W speakers. If I use a Connect, will I be able to feed whatever I play on the Arcam back into the Sonos system ie creating another source?

Any help appreciated

Thanks