Roger, of course I agree that things happen in between the microphone and the loudspeakers that alter the perception of the recording - some intentional, and some not.
Aside from your assertions, I do not know of a single source that ascribes any perceptible alteration of the signal to doppler distortion in amplifiers. Based on your description of this distortion, and published psychoacoustic research on human hearing characteristics, I do not believe the distortion you propose would be audible even if it did exist.
Duke
dealer/manuacturer