I just read your review of using the Townshend pods under your Thiels.(I own Thiel 2.7s as you may know from the Thiel thread).
It was very interesting and was a fuller description of what my own experience hinted at.
I tried some de-coupling type substances and pucks under a couple of my speakers. It did change the sound a bit. But one thing I noticed was less "floor feel" to the bass, and a change in tonal character in the bass, just as you noted.
I found I ended up preferring the speakers directly on the floor, even without spikes, as it gave more feel for the bass.
Sometimes we audiophiles are on such a mission to "reduce resonance" and have ultra clean sound that it can in some cases produce a more distanced "sound for the intellect" than the type of blood and guts impact we often grew up enjoying.