Granite surface plate

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?

Whether or not it works well I strongly advise against using a granite plate as an equipment stand. This explains why. From a Clients system

Good Listening

Peter

Ass soon as you get it, bend down to 3" tall.

If you look at the range of hardnesses in turntable materials, granite is probabably harder and denser than any of them. In other words, its mechanical impedance (resistance to being set in motion by external vibration) is high. This is not what you want for a turntable base, as it will take the vibrations transfered from the turntable and bounce them back into the turntable to be picked up by the cartridge, effectively raising the noise floor of the extracted signal. A turntable base should absorb and dissipate the turntable vibrations.

I've gotten much better results from a butcher block style maple cutting board. Mine is 3.5" thick and audibly lowered the noise floor when I placed it under my turntable. You can spend a lot of money on a butcher block cutting board or save a bunch by getting it from Overstock.com. It will likely be much less than a finished solid maple board, and the butcher block construction breaks up resonances.

MIne is just like this one.