just to clarify:
The EQ feature is meant for listening at reduced levels, say late at night. Since I rarely do this, I should turn it off and go flat
Dynamic EQ is not just meant for extremely reduced levels; ANY TIME your volume dial is below "0" (i.e. "reference") then Dynamic EQ is working to maintain the tonal balance of your system. It should improve the listening experience at essentially ANY volume level, although the effect will be more dramatic the lower the volume gets.
In most circumstances, Dynamic EQ should be left ON at all times unless you encounter a source with a screwed-up "reference" level (e.g. a poorly mastered video game, TV show, or certain music) where it sounds cruddy with Dyn. EQ on.
The point is that MultEQ + Dynamic EQ work in tandem to ensure proper "reference quality" tonal balance at any volume level. MultEQ corrects for the room/speaker acoustic environment to provide a "flat" tonal response at reference volumes; Dynamic EQ maintains this tonal balance as the volume drops below "reference".
The Volume feature is meant to handle those annoyingly loud commercials - this is obviously not needed if you are watching a DVD/Blu-ray.
the Dynamic Volume feature is NOT just for commercials; that is simply the most obvious application. The point of Dynamic Volume is to control wild swings in "loudness" in any type of content which would have you jumping for the remote control. This could also include DVD/Blu-Ray -- for example, most married men have experienced the "turn up the volume to hear the dialogue and then quickly try and turn it down when the explosions start booming before the wife yells at you" scenario.
So saying Dynamic Volume is only useful with TV is not doing it justice; it will really depend on your listening environment and habits. If you can crank up the volume and don't care how loud the explosions are, no problem, leave it off. But in ANY situation where you find you need to constantly adjust volume (e.g. explosions vs dialogue) then Dynamic Volume could be useful.
The point is that Dynamic Volume is constantly monitoring the content and making decisions about when to let the full dynamic range work and when to restrict it; in this sense, it is a much more sophisticated and effective system than simple "Night" modes which basically do a "dumb" compression of all content. Dynamic Volume is intended to allow you to not have to compromise a rich, full-sounding surround experience when you need to compress the dynamic range.
I personally use Dynamic Volume for all TV and movie content. If I am watching movies with my wife I will leave it on "Evening" mode as it will still sound great (full, rich, and bassy) but the sound effects are not so overwhelming that my wife yells at me. I can watch an entire movie with my wife without having to touch the volume control, which is the whole point.
I almost never use Dynamic Volume with music content, only when it's really late at night and I want to avoid waking the wife up. It actually does a surprisingly effective job at allowing the music to sound "uncompressed" while still keeping the overall "loudness" at a manageable level. But that's a rare thing...
Basically, experiment with Dynamic Volume and see how it works for you in various contexts; do NOT assume it's only for TV commercials!