Granite surface plate

I can post pages on that experience but the short answer is putting that much mass even slightly above the floor invites oscillation.

Think of an upside down pendulum. It's especially bad for turntables, less so for preamps but it has a sound that once identified is annoying.

Granite surface plates are a good idea that never quite worked out, at least for me. I don't know where you live but I still have one or more here that you may have for free.

Try a 2" thick slab of Delrin.. did wonders for my table. But not cheap.. around $1200

I agree with Albert. I've tried them on numerous occasions on many different components and they ring like hell.

They do look pretty. Wish they worked/sounded better.

If you like the look of it but want better performance I suggest you try a material like Corian, which is far more dense and damped than granite or any natural stone.

Surface plates when purchased from machine equipment suppliers are inexpensive. As other have noted, putting a heavy surface plate on the top shelf could cause a pendulum effect. You do have an option of counter balancing the pendulum effect by placing additional surface plate on the lower shelves.

How is your floor suspended?