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.