Just take a peek at the above link. Reading what I have researched on granite and its use with speakers, it seems as if it's actually preferred. It is one heck of a dense material, it's heavy and an elite handful of high end manufacturers use this material. I have yet to hear of anything bad besides a ringing. Braced and mounted properly, I don't see how this could be an issue. Consider the current material. MDF with a veneer.