Sorry, I missed your question earlier! Yes, I would recommend not trying them until after doing P90X. Although, now that I said that, I think you would be fine to sub in the Kenpo + and Interval + if you wanted to change things up a bit.
So far I've done all of the workouts except Total Body + (that's on tap for tomorrow). Abs/ Core + is an awesome workout, you do a cycle of 4 types of ab work- some hanging on the bar, some floor work, some standing, etc. There are some good variatons like Banana Twist (kind of like a banana roll & mason twist), Cherry bomb, etc.
Also.... for anyone that has ordered through my site. If you are already a member of the MDB club or have ordered through BeachBody in the last year, then you have already been assigned a coach. (even if you didn't know it!) So even if you order through my site, your *coach* will receive the commission. If you want *me* to be your coach, send me an email & I'll tell ya what to do! Thanks so much, I really appreciate it!!