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
I have tried a number of solutions, stone slabs with Nordost Pulsar points, herbies big fat dots, spikes etc. The best I have found is Symposium svelt shelves, Rollerblock Juniors. Better base definition in particular, but not earth shattering
I use Outriggers and find them to be excellent. They are also a lot less expensive than most solutions. I can't see any advantage that Sistrum would have.

http://www.soundocity.com/

http://forum.audiogon.com/cgi-bin/frr.pl?rspkr&1212931697&read&3&4&

http://www.audioholics.com/reviews/furniture/speaker-and-display-mounts/soundocity-outrigger-review
With Outriggers, do the speaker rest directly on the flat metal plate?

With Sistrum platforms, speakers sit on three brass cones which are fixed onto the brass plate.

I can't say how one sounds versus the other, but from what I can see from the Outrigger photos, they do not appear to share the same structure/design.
Do you have any options as to the positioning of the speakers, with regard to how they 'load' into the room, i.e. short wall, long wall.
By placing the speakers so that they a firing in the same direction as the floor studs, (assuming it's not on a slab), you will help the bass to develop; whereas firing across the studs, breaks up the bass.
Years ago, I experimented with speakers in this regard, in my Audio store, and asked people to listen to the speakers positioned in opposing directions, cross hatch, and then, firing with the studs. With normal bass output speakers, it was unanimous--that is everyone preferred firing along the floor studs. Interstingly, no one knew exactly what I was experimenting with--so it was like a blindfold test in some ways.

The outriggers are really good. AND, as theaudiotweek points out, the Sistrum work very well. I was not convinced until I tried them in my own system.
Gents

I can tell you without an audible doubt with my ears and two other pairs in audience that tighter coupling is more benefical than that provided by leveling. Unless you use additional added shim or shims of the same material you will loose coupling integrity with any leveling system I have encountered. The benefits of this maximum contact are better bass weight and midbass speed as well as greater image resolution. The last statement of vision would make you think my speaker was precisely level when in fact it was not, it was however precisely coupled to all surfaces. Tom