Sns, since my experience is limited to using the Muratas with the Beauhorns and then the Acapellas, it is hardly generalizable. Earlier when I had Altec VATers, however, and tried the Ionovacs with them, I did have unsatisfactory interactions in the top frequencies. I had assumed it was because you could hear music from the Ionovacs, which came down to 7000 Hz, if I remember correctly.
Faziod, mine is the same experience, at least so far, with the Muratas.