The speakers are not sibilant in the least. The onlly mention I have heard of sibilance is a thread buried somewhere in th e forum (search on "sibilance") from quite a few months back. If I remember correctly (like THAT ever happens anymore
), the sibilance was slight and the resolution was entirely resolved by repostioning the VP150 a few inches forward or backward in relation to the M60 fronts. Long story short - sibilance is a non-issue.
If you want a feel for the M60s, go listen to some B&W 703s - they are virtually identical (703s are 3X the price of the M60s). You won't find anything to listen to similar to the QS8s - nothing even approaches this fabulous animal.
To underscore Randy's point - Axiom just gets it right.