a couple of things to think about
corian is a brand only supplied by dupont but there are others out there just like them but not as well known.
the one I get from my local kitchen guy is staron
they usually have small pieces that are cut offs so stop by and ask them if they can spare some.
solid colors especially white is better than speckled.
as far as lexan or plexi you do not need to go deep at all as long as the whole carving goes below the surface so it is all frosted (even if there are small areas that did not go in just scuff them in the same direction as carving and they will not be able to tell). this is the most common material I use and it gives great quality and detail.
good luck
Tim
I know there is no point in reinventing the wheel, but reinventing myself is a worthy goal to be sure.
Tim