Jason,
The Dragon Plate you want for firewalls is the plywood core. The plywood is ultra high quality with a bunch of thin lamenates which makes for a light weight ultra stiff firewall.
But for those that just have to have the best...here you go:
Only 549 clams for a 12 by 12 sheet!
<a href="http://dragonplate.com/ecart/product.asp?pID=5148&cID=166">
http://dragonplate.com/ecart/product...48&cID=166
</a>