Sorbothane is ideal in my book. If it's done right, you can couple the speaker to the stand for low frequencies to get very tight bass, but isolate/damp the cabinet at higher frequencies (this is possible because the resonant frequency varies with strain). Cost is about $25 to buy a strip from mcmaster.com - item 3462K12 - and it just needs to be cut to size depending on the weight of the speaker. Several people on audioasylum and hometheatertalk have followed my suggestions and were very impressed with the results. Email me if you have any questions.
-Gary
-Gary