Any thoughts on a solid hickory platform under my tt

That's why I mentioned rosewood as the next wood I would try after maple. Then cherry. Both are musical woods. Mahogany is another wood worth trying, would probably be too warm for my set-up. The place that you mentioned has purpleheart block for about $500. That's what I said - exotic wood is expensive if you want to compare even a few. I might try cherry, even if the difference was small it would be worth it. And if it makes things worse, well, I could use an excellent cutting board in the kitchen.

A suggestion:  If it's density and stability is what you seek, you might try stone.
My shop (not audio, sorry) is next to a countertop firm.  They generate an enormous amount of 'drops' from their projects, many suitable in size for any tt/arm combo.  If you can generate a drawing showing what you want, they can make it.
And with the range of choices in material, pattern, and colors you could make something really exquisite for about what you'd spend on a wood one.  Not that wood isn't lovely, but...

asvjerry,
isolation yes....
looks? sorry but yes again....
nuetral or even slightly warm yes again..
I use to be a woodworker among other things,i still have freinds who do corian,granite etc on the east coast but the cost to ship is wicked out west. alot of these companies ship cutting boards for free custom sizes.
I do like the look of wood all my other stand shelves are blackand steel..

inna 
we have seasoned 3'x4' 2" thick top on our prep island in the kitchen ..hmmmmmm :)

Oleschool, you are not thinking of tearing it off and trying it under your turntable?