Interesting results pretty much in line with would be expected at reasonably loud home listening levels. You should keep in mind however that the numbers I previously mentioned were per speaker. For example, your 97dB stereo number could result from the two speakers each playing at 94dB simultaneously. When you double the number of speakers playing at a given sound level(doesn't necessarily have to be the identical sounds)the net result is 3dB louder,i.e., if one is at 94dB, two of them result in 97dB and four in 100dB. If that one speaker used 1 watt for 84dB(pretty typical)then it would use 10 watts for 94dB and four of them each playing at 94dB would reach 100dB(about your all-channel stereo number with maybe another dB added for the fifth speaker). The point therefore is that in the situation you described the power per channel may be more like 10 watts rather than 30 watts.
