I am in the process of removing the tile around my tub. This is tearing out the wall, and so I will need to replace this with drywall.

I have guys coming in to install a Corian surround for my tub/shower. What should I put up? I know of greenboard, but I have also heard of concrete backerboard, although that seems to be primarily for ceramic tile. I am only going to replace the wall about half way up, because the tile only goes up the wall from the tub about two feet. Any recommendations?