I think maybe moving up in speakers to something like a pair of used Paradigm Studio 20s would help in your case more than improving the power. They'll produce an excellent soundstage and imaging, something the Klipsch are not all that great at (I own some KSF 8.5s).

You could go the route of adding an amplifier, but I don't know how much of a difference that will make on speakers like the 10.5s. Don't get me wrong, I think the 10.5s are great speakers and almost bought them (long story, but went to buy the 10.5s for $400/pr at tweeter, but parked in a towing zone, had to pay the guy $100, and ended up buying the 8.5s for $300 since I didn't want to leave without a pair of speakers, back in college), but they are very efficient horn speakers that I don't think would benefit all that much from more/better power. I think the 10.5s are better suited for HT use, not as great for music.

Depending on how your Denon is (what model, 3300?), you could continue to use that and add the Paradigms or another pair of speakers that better projects a soundstage than the Klipsch. Of course, if you don't have a sub, you'll need one with speakers like the Studio 20s.