Hi @maxpayne,
Thanks for reaching out to the Sonos community and for letting us know about your concern. Let me share some information with you.
The Connect Amp works with traditional 8-ohm bookshelf speakers as well as pairs of 6 or 4-ohm speakers. You can add 4 speakers with the Sonos Connect Amp. Make sure the impedance rating of your speakers is 8 ohms. Any other impedance rating may cause the Amp to fault. We do not recommend wiring your speakers in series as it will result in poor sound quality.
The Connect Amp will only able to play one source of music at a time. If you're using four speakers and they are in different rooms, then all rooms will play the same music. Using a speaker selector switch is not recommended for it may or may not work with Sonos. Let’s see what Community members have any experience with this product with their Sonos they might share their inputs about it.
Please let us know if you have any further questions or concerns, we’ll be glad to assist you.