Calm levels (30%): 65-75dB peaks
Regular (60%): 83-90dB peaks
Stadium Levels (10%): 95-110dB peaks
For many, people will either listen louder or softer because their systems render tonality differently at different volumes (e.g. a tube preamp's volume will can determine the amount of "tubey-ness" and often sounds better starting at 11 o'clock"). But for really great systems, tonality, coherence, and realism are retained regardless of the system.