I thought the lower trim limit was -12 dB but I may be wrong. My concern is that, if the "real" value required is say -15 dB, then correct amplitude balance cannot be achieved among the speakers because the attenuation limits at -12 dB, and there is no way for the user to know how far off from ideal the gain is in the system. If the limit of the AVR is -12.1 dB then there is no concern (except very little margin). I am also concerned about the implications for the internal filters with respect to gain and amplitude optimization through the filter chain but have no way of knowing exactly how Audyssey handles that internal. Optimization of signal levels through a cascade of filters gets complicated.
I would not be concerned about a -9 dB trim level if the limit is -12 dB.
I would have the same concerns if Audyssey set the level to +12 dB, implying the amplifier did not have enough gain to balance levels among the speakers. Similar analogy; if a channel needs +15 dB, and the limit is 12 dB, that channel will be be loud enough relative to the other channels,and there is no way to know how far off it is.
HTH - Don
"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley