\rHi Mark:I would suggest returning the SMP300 in exchange for our XMP300 2 channel stereo amplifier. The Atrium Sub 10 has an internal crossover already, and most likely the sub output from the DENON should be an LFE (Low-Frequency Effects) where the DENON controls the full process low pass signal. You would connect to speaker A a stereo right and left stereo signal. Otherwise, before you do that, you could combine the SMP300 to just one of the inputs. I believe each voice coil is rated at 4 ohms and then wired in Series together to create an 8-ohm connection, but before you do that check with Polk and see what they say. Please let me know which option you might take.TL/5668\r