Muay Thai the next best thing? It's a step up my friend!
In a few months you are gonna be grinning like a loon with your progress! 5 years kickboxing will give you solid hands and kicks, so you can just focus on getting good knees and elbows, and working your low kicks (not sure if you've done them). Muay Thai is considered by most the most effective of all stand up disciplines because of the way it utilises everything you have an offensive and defensive weapons. You've got elbows and knees, you'd be a fool not to learn to use them!
Further more, I don't know what the Muay Thai gyms around your area are like, but I know that traditional ones are a rarity. I train with a traditional club, Jaruenmong (King Cobra) and we take the cultural side of Muay Thai very seriously. I know some newer Muay Thai gyms focus only on the combat side, simply for the sake of MMA fighters (beware of these places, the treaching is often a poor standard, at least in England) but the traditional clubs are the way to go forward. If you got a good club, you will probably find yourself doing a bit of meditation in with your stretching, you will find that your Kru knows a bit about the spiritual side of the warm up exercises (my instructor, Master Sean Dooney) is quite well versed in the Thai form of Yoga, he seems to know an endless variety of stretches, each one seems to have its own story! You will also be learning the Ram Muay! It's a beautiful thing, I think you are gonna love Muay Thai man!