Are you planning on using the CLS's in a home theater setup, or as a stereo setup?
Do you have any subs?
Do you have an old stereo pre amp?
What's your price range?
Does your Denon AVR-x2400h have an option to roll off the main speakers and pass the bottom to the subs?
My used Anthem AVM 30 preamp($300) has that option. It reduces the CLS driving load.
Your Denon is listed with 95 w @ 8 ohms(20-20khz) and 185 w @ 6 ohms(@1kHz), not sure what it really does at 4 ohms, much less 2 ohms. You really want an amp with increased output at 4 and 2 ohms for the CLS.
I've been using ClassDaudio SMA power amps ($650) to drive CLS2s and I am now driving Magnepan LRS and 0.7 speakers with ClassDaudio amps.
I've found good used stereo preamps, but very few listings for used power amps.