One thing I suggest, if possible, it to try switching out cables with both the Classe and Plinius. I run a Plinius integrated with Dynaudio contour 1.8's and found that cable matching made a world of difference. I use a Harmonic Tech Pro Silway interconnect and Audioquest Argent speaker cables. I found with the Harmonic Tech Pro-9 speaker cables, the sound was a little as you described- bloated and rich. The Harmonic Tech interconnect brough richness into the system and the Audioquest added some balance.
I'm really suggesting this since our systems are fairly similar. Of course, if you don't want to change the cables you have, you've got to match the amp to the system. I find that the Plinius is a very clear, neutral sounding amp with a real alive quality to it. Mine is a few incarnations back from the 9100 so I'm not sure how the newest version may compare. Trying out different amps could be interesting with some cable matching too if you're really looking to complicate matters!
I'm really suggesting this since our systems are fairly similar. Of course, if you don't want to change the cables you have, you've got to match the amp to the system. I find that the Plinius is a very clear, neutral sounding amp with a real alive quality to it. Mine is a few incarnations back from the 9100 so I'm not sure how the newest version may compare. Trying out different amps could be interesting with some cable matching too if you're really looking to complicate matters!