@patrickdowns: Watch USAM for a set of used Townshend Audio Seismic Podiums or Bars, they come up for sale pretty regularly.
For a cheaper alternative, if your speakers have narrow enclosures with a base that extends out in all directions (front-to-back and side-to-side)---or bases that are "outriggers", you can use sets of Seismic Pods instead. The Pods may simply be placed at each corner of the base, or even bolted onto the speaker base or outrigger, in the holes provided for the stock spikes. The Pods are far cheaper than the Podiums and Bars, and equally effective, assuming the speaker base or outrigger is big enough.