Wait, wait, waitaminute. Joe Flanigan as Calhoun? Sorry, but as much as I like Flanigan, he's too nice-looking. He really doesn't have the tough-guy image Calhoun is supposed to have.
Well, I think the main reason people go for Flanigan as Calhoun is because he bears a strong resemblance to the model who has always been used for Calhoun on the NF novel covers.