David, although this is an area in which mythologies flourish, there is insight of a factual nature available. The first point is to understand that any amplifier, regardless of the specific technology, only adds voltage from its power supply section to the weak incoming voltage to make it sufficient to drive speakers to loud levels. For example, if at a particular instant in time a tenth of a volt is incoming and the gain of the amplifier is a typical 28.3 times, the output voltage to the speaker is 2.83 volts. This results in 1 watt being used by the speaker when the impedance is 8 ohms(Ohm's Law; voltage squared divided by impedance). This is all that any amplifier with claims to high fidelity does. The sound isn't colored in any audible way, it's just made louder.
Having the voltage added in a tube rather than a transistor doesn't necessarily result in a flawed "tube sound" when properly designed. As the editor of the Audio Critic nicely summarizes in
"Electronic Signal Paths Do Not Have a Personality!" , competently designed units amplify transparently. However, design inadequacies can creep into many tube designs, especially in having such a high output impedance as to result in frequency fluctuations when speaker impedance fluctuates. Dr. Toole, in discussing this in Sound Reproduction at p.423 states that: "To reviewers these are moderately discomfiting numbers because the inevitable conclusion is that tube power amplifiers, as a population, cannot allow loudspeakers to perform as they were designed"; and at p.425: "In summary, with tube amplifiers, the internal impedance is already so high that damage is done to the frequency responses of loudspeakers having normal impedance variations".
Of course, there is a small but at times highly vocal(and unfortunately sometimes rather strident, as we've witnessed) minority of listeners who claim that mysterious benefits appear when a tube is used to add the voltage. The fact that there's no credible evidence to support this is ignored. The classic
Stereo Review blind listening tests still stand unchallenged(by real evidence, not just stubborn disagreement)and among other items showed that the $12,000 pair of tube amplifiers was indistinguishable from the $220 Pioneer receiver. Note in particular the detailed and sometimes flowery descriptions at the end of the article of the sound differences claimed before the blind sessions began and the brand labels and price tags disappeared.
So, if a correctly designed high power tube amplifier is purchased, it can drive speakers such as the M80s well, but the purchase price would be significantly higher and long-range maintenance reliability lower than readily available solid state units. This doesn't appear to be a very attractive world to "explore".
