Best wood under audio components?

Depends what components and whether you are trying to damp the sound. Check out the comparitive hardness of woods here.
The harder the wood, the "harder" the sound. By harder, I mean more focussed, detailed and perhaps brighter. The softer woods will sound more mellow. But, as with anything, YMMV and different wooods can impart their own subtle color. 

There are 2 levels only on my rack. The top is the TT (VPI Classic 1), the phono (Gold Note PH-10) is under. Both of them are sitting on sandbox. Each sandbox has a tile placed directly on the sand. The middle layer is a tube, and I am trying to find the top layer`s material
I managed to get a maple board (Shun Mook) under my TT, so I am looking for the wood under my phono.

+Both of my studio monitors (Dynaudio BM5 Mk3) under their factory stand (sittin on sand)
 
What would be the wood of your choice? -not maple, not baltic birch ply-

Yeah, ideally depends on components and on what you try to accomplish. But the OP is not going to listen to dozens of woods under all his components. I would just choose Michigan Maple or maybe Black Arkansas Walnut and call it a day. In any case, what's under turntable is of course most important. I prefer natural materials, generally speaking.

The thicker the better, due to higher stiffness. I would choose a hardwood ply if constrained by budget or maple, oak, bamboo, etc. if not constrained. 2 to 3 inches thick would be nice. The wood board should ideally be placed on cones.

You should have included all the info in the first post!
I use a 1 cm thick piece of solid walnut glued on top of the birch ply plinth for one of my 401 turntables. It sounds great. See systems. I use wenge for my armboards on the recommendation of the man who made my slate plinth so you might look at that.