Leave the amps add a matrix, control with RTI
I like knox media flex with volume control built in. However no 2 way on that yet but no biggie.
I don't mean to sound like a jerk but if you are doing a house this big and having to ask on this site how to set up multizone you may want to bring on someone with you that can help you do system design that has experience with bigger systems. Everyone will give a differnt oppinion as to what to use and everyone will be differnt.