On some Denons they have a feature what is called Night Mode. If activated it limits SPL and dynamic range and if you would try to crank the volume with it activated the speakers would definitely sound strained. I have not looked up if your Denon unit has this or not. It should also have a feature called Dynamic Range Compression. Check to make sure they are turned off.

I’m armed and I’m drinking. You don’t want to listen to advice from me, amigo.

-Max Payne