Well, the best way to decide what class to take next, is to ask yourself what you feel you lack or could improve to make the diving you see yourself doing safer or more fun.
If your navigation is weak, you could take a navigation class. If you want to refine your buoyancy, trim, and non-silting propulsion, you could take a cavern class (although that requires traveling to where there are caverns, which may not be that far for you).
If you want to push your own diving skills to a new level, and measure yourself against a tough standard, take GUE Fundamentals -- you have an instructor,
Ed Gabe, right there in Kentucky, and his reputation is excellent. Since you are already diving a backplate setup, at most you would have to put some kind of long hose on your regulator, and a bungied backup, to do the class. That's a small investment for an excellent class.
If you decide afterward that GUE diving is not your cup of tea, at worst, you will come away with some new or some much more polished skills, and some heightened situational awareness. At best, you will find a style of diving that suits you, and a whole community of people with which to do it.