Kimba, CTX is without a doubt the best used tapes in my collection. They're so versatile and there's so many ways to use them.
That said...
I remember from previous posts you have said that you sometimes have problems with high impact. The cardio in CTX is VERY high impact - fun, but high impact. So, you can either take care to modify, OR you can do a schedule where you only do 3 cardio portions a week, and double up on the strength portions
eg. Step N Intervals (chest) plus triceps from 10-10-10 one day, Power Circuit (back and legs) plus biceps from Kickbox.
I did my first week of CTX last fall as is, then soon modified it to a schedule like this. It also gave me an extra day for a long cardio, or yoga, or whatever.
Also remember that Power Circuit has a leg workout included as well as back work, so don't do it the the day right before or after Leaner Legs.
And last, leave All Step for the last cardio tape you try! It's by far the hardest choreography wise (IM0) so build your "vocabulary" and confidence with the other tapes first, then do that one last. It's super fun, but can be frustrating the first time through...hang in there.
Most of all, have fun! They're a blast. The only reason I'd ever get rid of my CTX set is so I can get the DVD!
Sophie