I do P90X, and I love it! I started P90x a little over a month ago with my brother after having been off exercising for a long time, and, while it is definitely challenging, I am not having any issues with it b/c of my weight. Truthfully, to me, it is no more challenging than working out with a trainer. I'd say my heart rate stays within the 60-70% range during weight days and 75-85% during plyo days. I'm not sure about the KenpoX day offhand.
Whether you'll have issues with it really depends on whether you like lifting or using mostly bodyweight exercises, or how much you like cardio, etc. P90X is a split of cardio and weights, and while it is marketed as something for people who are "advanced" exercisers, there is a lot of room for going at your own pace. That said, I am a person who likes to lift, and there is a lot of lifting. But as far as your weight/size, you won't have any particular problems doing the workouts, especially given the fact that you've worked out with other fairly strenuous workout programs. I would suggest using bands for chinups/pullups and just doing as much of each exercise as you feel comfortable doing. Otherwise, I think you'll be fine.