Your denon 3808 should have plenty of punch for your speakers. From what you say it sounds like you may be missing some dynamics and system synergy. The pics of your setup show some room for tweaking. Nice gear btw.
I would focus on getting your room into better shape to notice great improvements for very little cash. In order of importance (and easyness) I would say:
1: Listening Position in relation to room boundaries
2: Front Speaker Placement
3: Subwoofer Placement
4: Bass traps and acoustic treatments
I am always amazed at pictures online of people with great gear and lost opportunity. Everyone can benefit sonically from setup changes. Biggest upgrade to do and one of the first I would say. Good luck.
