Any opinions on the Symposium Acoustics Platforms?

I am looking for some thoughts from those of you with personal experience using the Symposium Acoustics platforms. I am particularly interested in the following models: Isis Shelf, Svelte Shelf, Super Plus Platform, and Ultra Platform. The platforms will be used with a custom Billy Bags Pro rack with sand filled tubing.

For those not familiar with the product, here's a link the to their site: Symposium Acoustics

I was considering the Ultra Platform to place under my Levinson 23.5 amp. I would also like to try one of the other shelves under my Classe Six preamp and Levinson No.37 transport.

Happy listening!