Which support for underneath CD player?

A slab of corian w/ some vibrapods, or other sorbothane type feet.

Arcici AirHead!

You might try a set of Aurios Pros. They are expensive, but make an enormous difference.

try a $4 small inner tube from a kids bike or wheel barrow with something heavy on top (large book, slab of marble, etc). Its only $4 and probably the cheapest trial method you could do before investing in other methods...

I second Rgd's suggestion, except I'd add try it without the book or the slab of marble as well (just make sure the player is level), as you'd like to drain the vibrations from the player into the innertube as well as those coming from the shelf on which the player sits. You might try the heavy book on top of the player to add damping as well (I found a telephone book on top of a Marantz CD 63 to be effective in that regard). Different feet, shelves, etc. will definitely change the sound, often in a way you might prefer, but with tubed equipment I've concluded after a lot of trial and error that isolation from vibrations is the best route to getting the best resolution and sound. And Rgd's method is very cheap and effective.