Barnett at this point in his career is becoming very injury prone, i'm surprised this isn't mentioned more often, but he's only played 29 out of 48 games in the last 3 years and been on IR twice in that time.
At this point, I would go with Hawk(if he will restructure his deal, and I think he will) and Bishop, if for no other reason than reliability, both of these guys are very rarely hurt.
But I also like the idea of getting rid of Poppinga above all, the guy is certainly overpaid for a 2nd/3rd string OLB, esp when we have guys like Zombo and Walden who not only have more potential but simply outperform the guy.