@sbank
.."Maybe certain ss amps that struggle with low end frequency performance in other aspects result in the perceived lack of depth?"..
Yes. And, agree some of the solid state amps you suggested don’t struggle with it. Swap in the right Pass or Coda or First Watt and it becomes interesting again. Not all ss amps are created equal as we see here once again. The great amp designers with "good ears folks" around them truly get it. Spec measurement engineers only looking to reduce distortion, not so much. Or, back to the modest mono tube amps and whoop, there it is!