You might be able to get away with a simple 2-channel amp by using impedance-matching volume controls and a little Speaker distribution panel from Parts Express.

I'm using a similar setup with one pair of speakers in the kitchen and one pair on the patio (both with volume knobs) running from a very modest Adcom amp fed the Zone2 signal from my main system. It works great. I'm GLAD I ran all that copper.

bibere usque ad hilaritatem