Question on Sonus Faber GP's

Good Afternoon,

I have a pair of Grand Piano's, love them. When i first saw these speakers, they had some granite or soap stone or some sort of mineral slab product underneath them. Between that time, and the time it took to acquire the funds to have such a speaker, they are no longer sold w/ the "stones" any suggestions as to what I could or should use? Are they even necessary to have/use at all? Any input is greatly appreicated.

I bought marble tile from the local Home Depot and added a few felt furniture pads on the bottom to prevent the marble from scratching the hardwood flooring. Set the speakers on the block, mark the positions of the spikes with a washable marker. Use a masonry bit, drill a shallow dimple in the marble at each mark. When you finished, the spikes sit firmly in the dimples and the marble is cushioned from the flooring by the felt pads. Total cost about $30.