I've recently changed surrounds to a Marquis HD and two Studio HD's. My Proceed pro has 10-volt balanced LCR out's and the Procced AMP 5 requires 2.24 volts for full rated balanced output of 125 watts 8 ohms and 250 at 4.
With the extra signal headroom, I split the pro's center balanced out using a XLR splitter into two balanced AMP 5 channels and bi-amped the Marquis. The smaller Studio's are getting single AMP 5 channels.
I prefer pure 2-channel for most 2-channel recordings. My surrounds are primarily for videos, yet, had to meet balanced music demands. I chose similiarly loaded larger surrounds to match large front main's, especially for videos. In multi-channel DVD-A, SACD and DTS music, multi-channel timbre synergy of the Legacy's through the AMP 5 is very delicate yet robust. A optional L/R Surround mode transforms 2-channel into a thoroughly enjoyable 5 or 5.1 musical experience. I'm very happy with the multi-channel resolution from the Legacy's and Proceed front-end.