As you noted, the volume level can vary widely. Not only from source to source (e.g. DVD, CD, TV, etc.) but from material itself. For instance, some of my DVDs and CDs are recorded much hotter than others. All of the DVDs from the Lord of the Rings trilogy come to mind. I recall Telarc CDs are recorded a little hot too.

That said, I find that a nice easy listening range for two channel music playback is approx. -14db to -10db. If I want some more impact, or I'm getting crunk with a Lil Jon CD, I'm playing in range of the -5 to 0 db on the dial.

On DVDs, I usually play back anywhere from -15db to -5db. If I really want to push it (let's say a demo to blow away a friend or neighbor with Top Gun, War of the Worlds, or U571), I've gone as high as +2db.

And I've gone as high as +10db on LP playback; but that's because my tube-based phono stage doesn't have a tremendous amount of gain.

Even at my highest listening levels, I've never clipped my big Adcoms, so distortion is not an issue. Instead, it somes down to damaging my hearing.