I use and also sell granite slabs for speakers. Although, not the cheapest fix out there, they offer sonic benefits of deeper tighter bass and better soundstage. You can use your spikes but they cannot come in contact with the granite or the midrange might become matalic (I use and would supply custome wood spacers. Now if you are thrifty, I have been told that hockey pucks work just fine on their own (between spikes and wood floor) Good luck
