Multi-channel is great for surround-sound and effects but here's another reason to run it instead of stereo when listening to music.
My room response for two configurations is shown below. The blue trace is 2.1 channel stereo with a 40Hz receiver cut-off. The red trace is 7.1 channel stereo with an 80Hz receiver cut-off. The 80Hz cut-off removes the dips at 75Hz & 90Hz shown on the red trace. The multi-channel configuration almost eliminates the comb-filtering (the dips that occur every 25Hz or so on the red trace) that results from the wall that is 11 feet behind my listening position (see my room below).
BTW, my bottom-of-the-line Denon is putting out less than a watt per channel to achieve these SPLs.
