those were my first tapes too, Daffy!
Well, second, third and fourth Cathe tapes. Previous to that I had been using Kathy Smith, Karen Voight, and some Firms. Needless to say, acquiring MIS, MIC, Body Max, and Interval Max blew me away.
While I think it would still be great to get some of her older step tapes (I'm still slowly acquiring these), I don't really think you need to wait to start using the ones you have. Just don't do them all the way, and don't feel like you have to do the moves exactly the way Cathe and crew do!
It took me a while to work up to doing Body Max all the way thru. When I was starting out, I'd only do the step one day, then the circuit and UB the next, or even split it into three workouts. I've NEVER done MIC yet in its entirety. I did do IMAX all the way thru the first time with modifications, but really, you don't even have to do all the intervals when you're starting out.
One thing that's nice about these tapes is that the choreography is less complex and less dancy/more athletic than some of her other tapes. So they're still a good intro to her style.
Anyway - don't be afraid to use the tapes in the way that suits YOU best. Modify to lessen impact or intensity if you need to, maintain good form, and enjoy yourself. There are no video police around to insist you do it all the way thru the first time!
take care,
Sophie