Also, for striking, there are tons of things you could do. There is the most popular, Muay Thai, but there is (like The Don said, TKD). Also, I don't know what style of karate you did but Kyokushin Karate is similar to Muay Thai and will teach you the striking with elbows and knees too.
Most Kyokushin Karate schools don't offer intense training like Muay Thai schools do. Also, it's usually not full-contact.
You have a good foundation, you've done boxing for a while and you were a great wrestler (by the looks of it), so you pretty much know all the basics and more. Just need to put your legs to work, and keep working on what you've already learned.
Some Muay Thai, BJJ, and Judo classes should do it (if you're only looking to be good at MMA for sport-related reasons). If you can't really afford separate classes (they are
pretty expensive), just join a MMA class.