On my Sony STR-DE585 reciever, when on 2 CH mode, the sound is loud and clear. But when I turn it on DPL II mode, the volume drops a shade and it doesn't seem as clear..Is this the amp? Or is it the DPL II? And if it is the DPL, why is it affecting my mains?? Also, I keep my center channel in the OFF mode when listening to music, because then all the speakers go lower and alot of the sound comes from the center channel...What gives?