in my estimation, your question about why people prefer a topology that doesn't test as well as another is interesting. Testing and engineering are very important and we wouldn't have audio reproduction w/out them, but they are not the end goal for many- enjoyable sound is. Scientific testing is important to testing theories and circuits, but you can't listen to a scope trace! (at least not on my monster HP...) So those us who prefer SET simply think it sounds better to us and the amount of harmonic distortion doesn't matter. The tone of all music instruments, to the extent they vary from a pure sine tone, is "distortion" from overtones. Many great violins have a second harmonic louder than the primary in spectograms! The Hammond electronic organs have something like 9 overtones blended into each note to create it's "tone". All topologies can sound excellent if properly implemented, and everyone should listen to the one they like best that produces the power they need. The whole art of making guitar amps is creating the pleasing distortion, usually through overdriving, even though almost all of them are P-P.