Has any one else tried using thick marble slabs under their speakers?

[Luvin Da Blues]

I have thought about doing this.

One question I have, should you use spikes on a hard surface? I have my speakers on a hardwood floor (with a large area rug in front) using the rubber feet they came with.

I've always been under the the impression that the spikes are for carpeted floors and the rubber feet is to be used on hard surfaces.