Having just built a great stove out of firebrick, I'm not in a huge hurry, but I'm thinking my next stove will also be cast core. I found your post, Troy, after I watched this video:
I'm hoping to ride on the coattails of your question, soaking up suggestions. The criteria I'm filtering ideas with, are as follows:
1) Very Durable, especially in feed tube area
2) Insulative (keep the heat concentrated in the burn tunnel for optimal combustion)
3) The more eco-conscious and locally available the materials, the better
4) Cost effective
If it doesn't meat those criteria, I would be tempted to stick with firebrick.