Same here Marnatz SR6012.
Could be your all running low sensitivity speakers that are power hungry for db that needs more watts/voltage for SPL-db and the distance of the speakers as you lose db's over few feet and need more power or higher sensitivity PA speakers so sell the hi-fi and get some matched compact 12" 15" bass driver with HF horn and you'll hear more with less power.
Also there is a source level adjustment on AVR same I guess with the Denon or maybe most others?
Press set-up on remote look for INPUTS
Scroll down to SOURCE LEVEL and press button (oh no not that one Boom!)
INPUT/SOURCE LEVEL can be adjusted for each Video mode sorace input if the signal happens to be weak? Trouble is mots of you won't see the signal weak as you have no level meters device attached to the AVR but I can see some source signals that are very low on my input-level-meters.
Just use the remote left right arrows to increase or decrease form 0db. Use CAUTION if signal is high and the SOURCE is increased too High it will push the amp levels to near clip and the AVR will simply shut-down into PROTECTION MODE with red LED blinking. Press power ON button and AVR will turn back ON.
I'm running outboard gear so the Marnatz SR6012 are not being used but still the signal is still sent to its amps with no way to switch them off and I noticed few nights ago a PROTECTION MODE shut down but forgot to reduce INPUT SOURCE LEVEL down to 0db for Alien Covenant.
Maybe the manufacturer should place an ON/OFF bypass switch to deactivate the internal AVR amplifiers as the RCA will be used for outboard amplifiers and therefore will reduce a few power consumption watts. I mean I don't see the logic in spending £few grand for Marantz AV8805 I'm sure its all the bells and whistles but really XLR is as common as mud and XLR take up far too much space over a D25 connector that has the same function of unbalanced/balanced and more D25 can be placed on the AVR and everyone can have 30 or 60 channels at the same low price of under £1 grand. That's my beef with these AVR/AVP in this market.