the mrx is not very good on 4ohm load my m80's, vp180 + 2 pairs qs8's and rated 75 watt on 5 channels.. the denon 150@4ohm each channel.. and the denon 4802 (as per the manual) has this special rare feature ''ext. in'' ... these jacks are used for inputting signals from a multi-channel outboard decoder no different than hooking up an exterior amp like an emo or d-sonic