What should be under my speakers?


I have Sonus Faber Grand Piano Home speakers in a 20' x 17' room with wood floors. The speakers have spike feet, and each one is sitting on a 1 inch thick, 12" x 12" slab of granite. Each piece of granite has a square piece of carpeting under it, as a further buffer. I know I probably could figure this out with a lot of experimentation, but what impact is the carpet likely having on sound quality? Would it be better (Subjective, I know) to have the granite slabs sitting directly on the wood floors? How would the sound change if I ditched BOTH the carpet and the granite? I would like to maximize bass impact, because these speakers are a bit thin in that regard. Thanks.
gipp
This has a simple and wonderful solution. Star Sound Sistrum stands will improve your sound by a large degree. Look at the Star Sound website for the best Sistrum stand.

They will just amaze you as the work great!
Post removed 
I placed them (Sistrum) under my Dali speakers and the sound become far more transparent, focused and composed. The bass was far better controlled and articulate. Loved them!

Your experience may vary.
Just wanted to give more info on my experience with the Sistrum SP-004 and SP-1 stands.

My Dali Grand speakers were 100lb floor standers with 2 bottom mounted 8" woofers per speaker. Bass was at times heavy and just a tad slow. Very warm and slightly midrange forward tonal character.

The SP004 units delivered a very noticable improvement. In fact, in the order of a very expensive wire or component upgrade.

As TVAD says they are expensive and can be found used if you are patient. They sell used for 1/2 the new price. I purchased Adona floor discs to protect the wood flooring. They cost much less then the Star Sound floor discs.

If you have any components on the floor these do the same magic under those components.

I suppose the improvement will depend on the speaker and room.
Post removed