You are on the easiest, simplest way to run audio to multiple zones. I can't speak to the in room volume controls as I didn't use them. I bought a speaker selector and ran speaker wire to four rooms in my home. I have run it off the speaker B on an integrated amplifier, off the speaker B on a stereo receiver, off the zone 2 of a home theatre reciever, and currently have a stand alone stereo (two channel) amplifier that runs the whole house audio. I have not had any problems with any of the set ups above. The speaker selector is doing it's job. I DO wish I had bought a volume controlled speaker selector which is just the s. selector with volume controls on it- my wife and I could then adjust each room accordingly.
Is there a reason you want volume control in each room? That is certainly nice, but does make install more complicated by far, imho. More expensive too. Used Niles 6 SSVCs (6 speaker selctors with volume control) are fetching $150 or so on ebay. I bought my simple 4SS for $25 shipped- it remains one of the best bang for buck audio purchases in my storied career.