So an update after playing around a bit with power chords and speaker placement:
First off, my feeling that the problem was related to amplification has to do with the fact that when there's additional mid-bass energy, it can be due to a lack of power in the amps decreasing the response in the lower bass. I still believe that may be happening, but was not at the "base" of my problem (so to speak).
The problem was simple...the Shunyata Venom power cable that I was using on the phono stage was somehow causing a mid-bass bloat. I found this out when swapping the Audience powerchord into the phono stage and putting the Shunyata back on the CDP. When I did that, the CDP seemed to have a bit of a bloat but vinyl did not. Seeing as I've been mostly listening to vinyl these days, I had not noticed that the problem was much more evident on the vinyl side.
So...I guess what I have found is that while the Venom is a decent inexpensive power chord, there is a reason that I paid the extra $$$ for the Audience. Also, the phono stage seems to be a bit more picky about power chords than the CDP, which might be down to the CDP having a better power supply.
My next step, I guess, will be to replace the Venom with another Audience chord, before considering mega $$$ equipment upgrades.
(Oh, and it wasn't speaker placement - they wound up right back on their little "x" marked out on the floor)