[S Clark]

Many years back, my students did a laser project with holographs.  Our issue was a highway about 70 yards from the lab.  We solved the problem with a truck inner tube with a pretty massive sand box mounted on top of it. 

[mcgsxr]

My fav trick to take most of the airborne vibrations out of the equation is the media closet - ie park all the gear outside the listening room.  I built one into my basement when we finished it off years back.

For actual speaker to floor - I ended up with 5/8 plywood over Delta MS - basically instead of using Dricore, we went with a 2 layer DIY.

Then underpad and carpet.

So likely not a solution for you for your speaker isolation desires, but it is what I did.  Very happy with it and my Maggies in my basement.