@godathunder, I think you are asking right questions. First of all, class D amps are measured in a different way than old A, AB, or B class amps. Then the distortion figures may differ a lot from manufacturer to another which offers a big variety to publish watts.
Watts are funny, because everybody understands one figure - that is only faintly related to loudness. Where are discussions about sensitivity (dB @ 1 W/m), loudness (dB), frequency response (50 - 4000 Hz ±6 dB) and so on?
The only reasonable way to measure loudness sure requires a system (amp + cab). Sometimes it would be very eye opening to arrange an open air test session where anybody could bring a system to the place and then someone with decent equipment and noise source would make measurements.