Thanks for the input guys. I am leaning toward the rubberized undercoating route. I agree that, although, POR-15 has a reputation for being tough, it should probably have some kind of coating over it for added protection.
I like the idea of using the bedliner material, but that stuff is so tough how would I remove it if I ever needed/wanted to? I had a bad enough time removing all of the factory undercoat and it wasn't as tough as bedliner material.
The one person I spoke with that recommended NOT undercoating at all was concerned about trapping moisture and causing more rust down the road, but I think that if I am diligent in applying the POR-15, this should be a minimal issue, if not a non-issue.