Looking for program recommendations

I've been doing FB Booty Round 2 and FB Flex Upper Body staggered together with an Ab day added in each week. I do not need to lose weight or lose fat. I like that the FB Booty includes HIIT because you get the benefits of cardio while building muscle and it doesn't seem to detract from my progress the way longer cardio sessions seem to. The faster paced (timed) workouts are a little difficult for me to keep up with sometimes because I am lifting pretty heavily. I'm looking for something that is similar to those two programs with abs included. I find that without the ab day, my core isn't strong enough to support the weight I need when lifting on my lower body or for some of the exercises that use the back and core (ex. bentover rows). I tried FB Burn and my body did not like it. Would FB XT or FB Mass be worth a try? Any other recommendations are welcome as well!