A lot of folks are overlooking O'Leary from Western Michigan. O'Leary and Benedetto are young guys that will be shooting up the coaching ranks. Walters is a young guy that already has a lot of experience, including a couple years as a head coach. All of them have done a great job calling the defense during games and would likely be a big improvement.
The JMU guy might turn out to be a good DC, but he was just fired from Alabama last season. Batoon at Missouri just took over Blake Baker's defense and hasn't had enough time to show if he's good enough to sustain it. Belk from USC is a rising star in the coaching ranks, but too unproven as a DC.