This should help you understand why the ADA made your system sound fuller pre-calibration at -20 compared to running off the Denon. The gain of the ADA is about 3dB greater than the gain of your Denon's amplifier. Stated another way, when you dialed -20 pre-calibration, you were really listening at -17.

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated