It would be interesting to see exactly what these different cables do to the sound. This could be done with a before and after measurement of the speaker. People say you can't measure these differences, they're something that only the human ear can pick up, not any machine. I just don't believe it. I was told that about amplifiers too but when I perceived a different sound between two amps, I took measurements of the speaker using the same test signal into the amp and the difference showed up clearly as a change in frequency response from the speaker. Mystery solved! Anybody ever measured their speakers before and after a noticed difference in sound quality after a cable change? It would give more meaning to your subjective descriptions to get an objective measurement of the change.
I think measuring the speaker's output is the correct thing to do because we're looking at the result of how the system is interacting with all of it's components, not just how one component operating by itself measures into a test load.