Another problem
is that 100watts is not the same between any two amps.

How is it not the same? It seems that is the point that people are trying
to
make... That it IS the same.

I'm not asking to argue, I'm asking because I'm curious... I know little
about
the subject really, but it seems to me that 100 watts is 100 watts.. no
matter
what its source.

100 watts IS 100 watts. But distortion content will differ between
amplifiers. However, simply put, it's too low to be audible.