Randy, give the multimeter voltage measurements a try at the shut-down levels. Yes, it isn't the way that amplifier output is measured professionally; among other things fixed resistance into a set of resistors is used(rather than a speaker), the frequency is known, rather than variable as it is with music, and an oscilloscope is used to observe the point at which the wave form top flattens, indicating clipping. However, this "quick-and-dirty" measurement is often used to get a ball park number. Don't worry about refinements at this point; it'd be interesting to see the voltage numbers at very high sound levels.

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Enjoy the music, not the equipment.