Existing system with Niles volume controls connection help
I just purchased a house that has 15 speakers divided into 8 zones connected through 8 Niles VCS100K volume controls with selectable impedance. In the basement there were three 4 conductor speaker wires and four 2 conductor speaker wires with all the negatives twisted together and all the positives twisted together that I assume the previous owner had connected all together into one channel of an amp. The volume controls are set to x8 impedance magnification.
I separated all the wires and connected them individually to discover that each of the three 4 conductor wires runs to one of the 3 zones in the basement but the four 2 conductor wires appear to be duplicates of each other. Each of them connects to either the right or left channel of all the remaining 5 zones.
Speakers are New Wave Audio C-650KV 80W 8 ohm ceiling speakers and 2 russound outdoor speakers I'm not sure of the model.
Why would there be 2 sets of wires connected to the left and right channels of the 5 upstairs zones? Any advantage to connected them both or should I just connect one set?
What size amp should I be using for the 5 zones? A 400W amp since it goes to 5 80W speakers or just an 80W amp? The volume controls are rated to 100watts.