Proac 3.8 or Sonus Faber Cremona

The Concentra and the Proac 2.5's or D15's sound great together. But it might help if you share why you want to change speakers. What are you looking for that you don't get with the EAII (which BTW,I also love with the Concentra)?

I think Fletcher-Munson has a role in what you're experiencing. Other than a separate subwoofer, as Aniwolfe suggested, allowing you to control the bass volume separately, or a tone control, I don't see a solution.

I also hazard to guess that the one thing that we rarely do, but should, when auditioning speakers is turn the volume down. Many speakers have a tendency to sound balanced at a certain volume "sweet spot" but colored at lower or higher volumes. Try it when auditioning your replacements.

Good luck.