Hello Chesseroo,
Hope you are well.
If using a Harman/Kardon with channel specific bass control you disable the crossover in the subwoofer and use the bass management in the receiver, this allows you to have different crossovers for different channels, as long as you have your subwoofer amp's crossover disabled or dialed to its highest setting. AVR630 has front/center/surround/surround back specific crossover settings, instead of one universal setting.
So, you can have your large M80's set to 60Hz, your center at 80Hz, and your surrounds at 100Hz if you wish, and the receiver will send the signals below those settings for all channels to one subwoofer.
I am not familiar with the Denon's bass management, I can only comment on what the H/K is capable of.
Unfortunately 100Hz is the threshold for directionality, therefore the reason most people recommend 80Hz or lower for the crossover.
Later,
TonyM
