If the Motion 30 and Motion FX have an impedance curve anywhere near the Motion 60XT, you may very well have an issue. See curve on 60XT's below;
If your AVR is only stable down to 6 ohm loads, dropping this to 4 or below, (as you can see, the 60XT's dip to just over 2 ohms in places) will cause the amps to struggle at best.
Just because an amp doesn't physically feel hot, doesn't mean it's not going to cause issues.
To quote the source of the above pic "Nominal impedance is four ohms, and the speaker drops to a low of 2.1 ohms; so, even though this speaker will play loud from just a few watts of power, you need an amp with plenty of current to drive it".
I had this exact issue with the previous amp I used to drive my Motion 60XT's. Even though it was rated at being stable down to 4 ohms, it struggled to drive the 60XT's. The symptoms for me were VERY pronounced, the top end was incredibly bright and very harsh sounding. The upper midrange sounded slurred and muddy. The bottom end was nothing on what I've heard from these speakers before.
Have since upgraded to an amp that could supply enough grunt to be stable down to 2 ohms and the difference is gobsmacking.
I'd be getting more info on the speakers and then passing this onto Denon (or a dealer) and seek their advice. Not a lot of point acquiring a bunch of rather expensive gear, if there are going to sound bad together, or worse, cause failures.