IsoAcoustics GAIA

I have the same Gaia II's under my SF Olympica III's and certainly experience the same sonic benefits you describe.  I also run SVS Sound Path subwoofer isolators under my Rel's.  With both of these isolators in place, I can now hear a defined bass replete with micro dynamics, harmonic resonance, and decay.  This allows me to easily follow and enjoy each plucked or bowed note on a double bass or like acoustic instrument.  These subtleties were missing before these feet were installed.  I listen to a lot of Jazz and Chamber music.

I tried them on my JBL ti2k and like you say the bass got a little tighter, but also leaner, and the mids and highs got a little harsher... I ended up sending them back and going to carbon fiber speaker spike floor pucks on top of high duro sorbothane rounds from Amazon for $100 all in and got a much better result than the $550 isoacoustics...

I say hard pass on isoacoustics, on my components I have Ganymede Isolation bearings which are absolutely amazing, but they are no longer made.

Yes. I use them with my stand-mounted Fink Team KIM speakers, and to similarly good effect. Aside from tightening up the base, the reduction in "smearing", which was previously unnoticeable, has had a very positive effect.

No harshness whatsoever in the mids or highs, and I would argue that reduced vibration would never directly have that effect.

Got them under my 200+lbs PBN MONTANA XPS speakers. Once you find a way to install them, they are so much better than the spikes they came with. Isolation is key, not coupling.

I installed them on my KEF Reference 1 stand’s, the difference was positive. Better soundstage and everything tightened up. Recommended for those with hard floors.