Best vibration isolation for speakers on carpet?

I use Townshend Podiums.

Townshend Podiums! Nuthin' else like 'em!

I had a pair of Revel F32 speakers using the spike feet combo that comes with the speakers. I bought 3rd party outriggers to replace the spike feet. Positive major difference for speaker stability. Bass clarity and detail improved as well though it was a minor improvement compared to speaker stability. 

Good thing you didn’t go with the Gaias because they are a nightmare with carpet, especially thick carpet. 
 

One thing I’ve learned over the years is that when leveling spiked speakers, you often have to adjust the spikes by only small fractions of a revolution (like 1/6th) in order to get all spikes firmly contacting the substrate. So you feel the speaker rocking at the top panel and think maybe one whole counter-clockwise turn of the short spike will do the trick when in reality it only takes 1/2 turn or less. 
 

Wooden subfloors make this even trickier because you have to account for the spikes penetrating the wood and over time they settle. In those situations you want spikes with a wide cone angle similar to the Dayton Audio ISO-4C. 

For those with speakers which incorporate outrigger bases---and for those who added after-market outriggers to their speakers, individual Townshend Audio Seismic Pods may be substituted for the spikes routinely supplied with outrigger bases. Good outriggers fitted with Pods are just as effective---and cheaper---than the Podiums (as well as the Seismic Bars).