The Denon has two sub-woofer outputs on the back. why would you not use one of them as it's just like the tape-loop out except instead of sending all the sound and then having the sub try and filter out the high frequency sounds off, the Denon does all that for you

Anthem: AVM60, Fosi DAC-Q5
Axiom: ADA1500, LFR1100 Actiive, QS8, EP500, M3, M3comp, M5