Come on man. How about the bass can get tighter, and less bloomy.
It's a bit like a sub with cabinet wall resonances. The resonances might be minuscule compared to the output of the woofer, but taking away the resonances sounds cleaner for sure.
Ok, that helps. I'm not trying to be difficult, just need more info to better understand your experience otherwise we may be talking about different things.
With IsoAcoustics stands I've had the opposite experience. Reducing the transfer of vibration using them has always cleaned-up the bass in the way you describe because it reduces resonances from the home and everything in it. Just like your subwoofer example, the output from my home is small vs the speaker's direct output, but reducing the home "singing along" with the music makes the sound cleaner.
I don't doubt your experiences but I do wonder how they could be so different? Possibly the design of the speaker cab and listening space... My experience is mostly in residential homes with modern construction, which is easily excited by audio systems playing at moderate to higher SPLs. Also, I do think vibration control devices can't be generalized because the effects are often very different. For example Rollo's dowel rods will only isolate in one dimension and couple in the other two. Ball bearings isolate horizontally but not vertically. IsoAcoustics stands do both, but maybe to a different degree vs many other stands. I can say that myself and others results from Iso stands seem to be very similar. This is why I ask what you compare spiking to? I think it is possible you compared it to something else that was not nearly as effective as Iso stands.
Typically, if we weren't dealing with audio, we'd have measurements that would describe attenuation vs frequency, which might allow some correlation of subjective experience with measured data, but of course we don't have that information...