I use granite under my speakers primarily to protect the hardwood floor. Results have be outstanding.
For what it's worth, I think granite would serve as a better base than marble - if you look closely at a slab of marble, in most cases it's held together with some kind of fabric. Marble is full of fissures and the cloth stuff keeps it from falling apart!!
If you are looking for something that is structurally sound, go with granite over marble - however the really pretty granite with buzillions of colors can be almost as fragile as marble. The "absolute black" granite seemed to be the strongest.
For what it's worth, I think granite would serve as a better base than marble - if you look closely at a slab of marble, in most cases it's held together with some kind of fabric. Marble is full of fissures and the cloth stuff keeps it from falling apart!!
If you are looking for something that is structurally sound, go with granite over marble - however the really pretty granite with buzillions of colors can be almost as fragile as marble. The "absolute black" granite seemed to be the strongest.