Thanks for the suggestions everyone. As to the MC2155, i haven't noticed it being "slow" as described in the Agon post. So far, it has been very musical and presented excellent base and dynamics. I had actually read that thread before taking the plunge on it.
To briefly respond, no added absorption, i/cs are all from Blue Jeans Cable, speaker wire is signal cable's ultra wire.
I'm thinking about the cabinet upgrade kit from skiing ninja and no rez. Seems like a good next step?
Also, I read about folks filling the bases of the x-sls with sand. Worth doing? Thanks again all.