I connected my remote to my PC and fired up the webapp through Logitech online, and the 5803 was already in their database for the 300! Interesting.

I added it, and it showed the button mappings and it exists, however it isn't working at all. Says it's set to the VCR/Aux button, which I've pressed, but nothing will power the unit on or off, or change any controls. Hmm, maybe I'm missing something? I hope the IR isn't messed up on my Denon.

One other thing is, when I press the power button the TV button lights up on the remote. I'm not sure if that's normal or not.