Rubber feet when mounting on stands

+1 for Blu Tack.

Loose the feet for coupling and better sound.Enjoy!

Herbies or ISO Acoustics.

I use the Thin Fat Dots that Dill suggested but mine are also bolted to the stands.
The decoupling occurs at the bottom of the stands which sit on springs.
Speakers = 105 lbs, Stands = 70 lbs
The situation may be different for smaller, lighter speakers where many use Blu Tack to secure them to the stands.

if you have the space on the top of the stands, I would strongly consider IsoAcoustics Orea Pucks.  I have Bronze pucks integrated right into my stands and it helps deliver a better image.