Cork,
As JohnK indicated, with the level differences in souce material--some CDs are recorded 10 dB to 15 dB "hotter" (louder) than others, so understand that the 0-dB indication on the receiver is very approximate.
Using a dB meter at your listening seat is really instructive. You can measure peak or average levels and equate them to the general subjective impression of most people: peaks at 95 dB or higher are considered "very loud". Levels around 85 dB are "quite loud" and lots of listeners set levels to average between 75 dB and 85 dB. We hear each increase of 10 dB as "twice as loud". A 3-dB increase is described as "a bit louder".
It's impossible to know exactly when your receiver/amplifier is approaching clipping, short of having an oscilloscope with a hold setting. Some amplifiers begin to sound harsh or strident as distortion increases. Certainly you should avoid setting the volume so that peaks at your listening chair exceed 100 dB SPL. By the way, the SPL meter should be set to the "C" weighting, and all of the levels I've talked about are relative to the meter set to "C" weighting.
Keep in mind too, that I've rarely measured acoustical music in concert halls peaking at more than 102 dB (that's with full orchestra and chorus in Carnegie Hall in a very good box seat).
Amplified rock is an entirely different story, and absurdly loud levels are often the norm---well above 100 dB in clubs and live concerts.
Regards,
Alan
