>>First i need some 'sibilant' source material. If anyone has suggestions of better known music and a particular track (or possibly a movie for that matter, our dvd collection is growing) that consistently has the sibilance they find nagging, i can try sitting off axis and do some A/B switching b/w the M40 and M60 to focus on the S sounds.

Agreed. The challenge will be finding material where the sibilance is "borderline", ie is subtle enough that reasonable people might suspect it to be caused by the speakers rather than the material. Any recording with blatant, hissing sibilance isn't going to be much of a test because everyone will agree that the recording is at fault.

So, folks... we need examples of those recordings where "Axioms show sibilance and Monitor Audios do not show it" (you get the idea).

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8