I got excellent isolation and resonance control with a rig similar to Tbg's last suggestion. Placed Vibrapods on the floor, a maple cutting board on top of that, then the spiked speakers on top of the board. Worked like a dream with increased dynamics and clarity. Got the chopping board at Bed, Bath & Beyond for about $20/each. I found that the wood worked better than granite. A cheaper, and better, alternative to the Vibrapods are V-Pads available from your local Heating and Air Conditioning supplier. They're about @$2.50 and you need 4 for each speaker under the board. V-pads are 4"x4" pads of about 1/2" of cork sandwhiched between two layers of ribbed rubber.
