How much amplifier power do you really need?

[Confused]

@David A - I pretty much agree with your comments above, but I think there is one additional point to add. The big take away I received from this thread is just how much difference the type of music makes to the demands placed on an amplifier. In an earlier post I linked to the Harbeth forum, which has a longer version of the video posted in the first post. In this slightly longer version the last two minutes the music is changed from the Electronic Pan Sonic track to a rather milder Corelli Sonata. The gain on the amp was left unchanged. The peak power used when playing Corelli was 28 watts, versus the 760 watts peak seen with the Pan Sonic track. So in this specific example, a simple change of music resulted in over 27 times the amount of power being required. From a more subjective perspective, it is interesting that nobody commented on the volume level when playing the Pan Sonic track, but the comment was made that "we were playing louder than we would normally play Corelli at" for the later section of music. So taking the exact conditions that the video was made, the room, the speakers, the volume, a 140Pro would probably sound very similar to a 1000Pro, whereas with the Pan Sonic track, the differences would likely be far more noticeable.

@RebelMan - the Archimego link is interesting, although I am not sure about the merit of testing with test tones at specific frequencies. For example, you might do the test with a 120Hz tone as suggested, and get a particular result. However, with a specific speaker the result at 60Hz or 200Hz might be very different due to variations in the impedance curve. So I think the proposed test might give you an indication of the power required, but only an approximation. I guess you could try the test using real music, but then the results would depend on the response time of the voltmeter used. I am not an expert with respect to voltmeters, but I suspect that the response time is typically somewhat less than would be ideal for this sort of test.

One other factor that interests me is the ability of a specific amplifier to respond to the required transient peaks in the music. In other words the ability to go from low volts / amps, to a very transient peak of high volts /amps. Subjectively, this is referred to as the "speed" of the amplifier. Technically this is known as "Transient Distortion", which is not something you often see in amplifier specifications, and is not something you could readily measure with a volt meter.