I think the frequency and the wavelength of a 40HZ bass note will remain the same no matter what. The wave will not move faster, that would change the frequency - the number of cycles the wave makes per second. The frequency of a bass E note is always going to be about fourty cycles per second and the wavelength is going to always be about twenty seven feet long. What changes when we add more energy to the speaker, watts, is that the amplitude of the waveform increases.

It might not seem to make sense, but frequency (cycles per second), wavelength, and the third component of a waveform - amplitude are involved. The amplitude is the variable that changes and makes the sound louder. Frequency and wavelength of a given note remain the same. In order to increase the amplitude there needs to be an increase of power at the speaker to make it louder.

For the sake of discussion this is interesting, but for all practical purposes it may or may not be of interest to a muscian, and definitely is not necessary to know in order to be among the best of muscians. It's kind of like noisy single coils - some muscians like them and some don't, and the reason why they are noisy doesn't really have anything to do with why a musician may have a personal preference. I'm sure there is more to the whole equation and what it means to how we hear sound, way more than I know.

For some people 100 watt amps intuitively sound great and others don't like them. You can turn them down or turn them up and satisfy just about anyone. And like Eric suggested, some muscians may not have any need for a 100 watt tube amp.