I think that's approximately the issue with my setup as well (I also have a Denon receiver). I believe I settled on only disabling CEC on the TV. Thus waking up the Apple TV does turn on the receiver, and putting it to sleep turns off the receiver. I only have to manually turn the TV on and off, which isn't so bad. Ideally I would be able to configure it so that all CEC controls were active except that manually turning off the TV did not turn off any other device.