I've studied a non-traditional form of Tang-Su-Do for almost 15 years now. Our style incorporates a lot, though, including Muay Thai, Combat Tai Chi, Aikido, Jiu-Jitsu, and Karate.
Whatever you decide to study in the long run, though, just make sure it is from a master that you can respect, and that you stay with it consistently. I would have attained my mastery by now if I hadn't had a rough patch a few years back. But hey, I stuck with it and am moving towards it with each passing day.
Good luck, study hard, and remember: that whole "if it doesn't work in MMA, it doesn't work" shpiel IS A LOAD OF CRAP. Most military forms are absolutely lethal, but as such cannot be adapted to MMA. An Aikido master is terrifying to face in the streets, but has no place in the octagon. Just don't be fooled by morons. MMA is fantastic, really, but it is not the be-all-end-all. Fifteen years of getting punched in the face has at least taught me that much.