Purchased a system. I have a Marantz 7701 pre amp, a Marantz MM7025 5 channel amp. considering adding a 2 channel amp to go from a 5.1 to a 7.1 surround sound. I know of the MM7025 (800 bucks). Looking for a very good, less expensive 2 channel amp that will hook up to my system and run the 2 additional surround sound speakers. Thanks, Brad