PS1: Forgot to answer your initial question about the AMS on-top (again 
): As long as the feet are not fully squashed but have some way to go, their spring constant is likely still in the linear range. So they should still be effective in the same frequency range.
PS2: Did you update to the latest Firmware? I have found that to make a hughe difference. I can still hear the printhead, but the Aux fan at 70% is significantly louder.