Speakers on speaker stands-isolation ideas?

IMO, you are approaching this the wrong way by assuming "isolation" as you call it, will yield a sound that is more preferable to you.  I'm a big fan of standmounts and I have consistently found that each speaker requires something different to adjust the sound to your preference.  You must also consider safety, as putting a speaker on a stand with no attachment subjects it to being knocked over.  But rather than think of isolation, I would first try the speaker on the stand with something like Herbie's black dots, then with Blu-tak, then with some hard interface - I've used casino chips, and see what sounds best.  Same thing with the stands.  Try spikes, try Herbie's Ebony Domes, which are also good under speakers, but allows them to move around.  I don't even think isolation is necessarily desirable.  I have found the stands to greatly influence the sound of the speaker, almost as if they are a part of it and sometimes coupling the two units as one yields the best results.  I think. 

I know we're talking sound here, but I have to again mention safety.  A painter knocked over one of my Opera Callas monitors held to the stand with Blu-Tak.  I was able to grab the unit by the speaker and the stand and speaker stayed together as one.  Of course my dog happened to be laying exactly under the speaker and would have been injured on killed had the speaker not been secured to the stand.  Keep that in mind.  As a bonus, it may yield the best sound as well.