I know what you mean about the efficincies. I have 102db for the fronts, 99db for the center and 98db for the surrounds. Will not having adjustable gain on the amplifier as I have bee a hindrance when trying to fine tune the levels to the best compromise for the hiss. Also, does the trim affect the apparent noise now in the new configuration. Meaning a +5db vs a -5db on a certain speaker will have a lower apparent noise because the overall volume level can be set lower?