Dan, what I usually refer to as "comfortably loud" is an average listening level of about 80-85dB, which is in fact loud. Some of the classical items which I listen to are very dynamic and might have split-second peaks 20-25dB above that, but as best that I can tell 110dB(or using 100 watts)has never been hit.
Most pop music has a rather low dynamic range(note the +/- 5dB figure Axiom mentioned for the range of the pop items that were used in their distortion tests), but if that -15 figure on your receiver does roughly correspond to 100dB at your listening position(except that you did say that the movie level was lower at the same settings), be careful.
