@j-wall Very nice system!
Changing the amps will change the sound, you can definitely try that! Audio Research Ref line is top notch stuff and the odds are there will be a good improvement sonically by switching to ARC Ref series components.
But…the room acoustics and speaker placement is something you will run into no matter what preamp or amp you are using.
I don’t know what what you mean by acoustic panels next to the speakers. What I would recommend is trying the following:
1. Spread the speakers further apart to about 1.5ft or even 1ft from side wall
2. Move the acoustics panels to treat the first reflection points (have panels on the side walls approximately midpoint between you and speakers)
3. Adjust the toe in to get the imaging to your liking. Adjust distance between listening chair to speakers.
4. I would also add bass traps behind the speakers
Suggestions above to move the rack are valid but I would focus on acoustic treatments before making any other changes.