Instead of the Vibrapods try Herbie's big fat black dots between the stand and your speakers. Very economical with a generous trial period. As already suggested try filling the stands. How much to fill them and with what is the experimental part. I've had good experiences with a combination of kitty litter and fine lead shot (#8 I think). If I get to a point where I need to fill stands again, I would try the micro bearing fill sold by Star Sound Technologies.
http://herbiesaudiolab.home.att.net/spkrfeet.htm#cone
http://herbiesaudiolab.home.att.net/spkrfeet.htm#cone