Gena,
This was an interesting test and it certainly continues to show how at average to moderately high volumes, consumers still only require relatively small amounts of power. However something is still missing from the equation (in practice) which may only be tested at the risk of damaging your system, something a friend of mine tried some time ago.
If i understand your measuring correctly, you hooked up a single M60 to test the power consumption at limited frequencies, then turned on all other speakers plus a sub and set the speakers back to 'small' before testing music (some inherent holes in the measuring by doing this, but easily rectified). Ayway, with all channels running, the amount of power consumed will actually be x times the wattage per each speaker. In your example of peaks ( and assuming the setup consisted of 4-M60s), 12W peaks times a 4 speaker setup brings the total consumption into a 48W range, well below the rated output for a receiver but about 50% of its rating, not 10% (and these numbers use the subwoofer "on", mains set to "small" power values).
Next take that 4 speaker setup and turn the receiver up to 100% (or maybe even less) and measure the output as it drives the speakers once distortion begins.
You may find that the total wattage consumed is still not beyond the rated output of the receiver (a guy i knew tested something similar). So if this is the case, how is it possible that distortion is present if the measured consumption 'should' be under the rated receiver power output?
Here's where capacitors and power supplies (size, quality) comes into play for energy storage/flow during sound playback and power consumption (rates vs. capacity). This is usually where receivers fall short of separate components...but again only at higher SPL, varying with room size, amount of low frequency energy being played, speaker size, impedance or the other usual suspects as to why a receiver drops out before separate SS amps.
I wish i could provide more details on the experiment but it was done quite some time ago and my memory is faded. I don't know the guy anymore.
Food for thought.
Incidentally, my listening preference for movies is often lower than for music. When i'm playing pool in the room next to the media room, my Axiom system can average 94-98dB at the seating location (about 11'). I only have a receiver at this point but will likely add an external amp for the mains to give me a bit more overhead as the 100dB point is approached, distortion can begin (on my system).
My larger Tannoys upstairs typically average 104dB (also at about 11') when i'm listening to them while cooking in the kitchen. I'm planning on getting a larger amp since the one driving them is incapable of overdriving them. I would rather have an overpowered rather than an underpowered amp for those pricey dickens.
