i think you should first use your Denon, and later on, if you find that sometimes you hear a bit of distortion - and it disappears when you lower the volume level - then this should be a sign that you need more power.
the same reasoning applies if you move later on and your HT room is larger than your current one.

See: http://www.blu-ray.com/community/gallery.php?member=Gelli
or: Axiom Gallery