Hi Reese,
There are actually two Tae Bo Cardio Circuit workouts. One is 30 minutes, and the other is about 50 minutes. The 30 minute one is faster and more intense than the 50 minute one, but I would say they are both pretty good. I love Cathe's Kick, Punch & Crunch KB (KPC) workout. The DVD one has great pre-mixes too. I do like KPC much better than Kick Max.
As for your question about which Tae bo workouts are closest to the older taebo workouts. Like Mona said, really the Get Ripped series is the closest one or even better than the advanced series. But there are some great deals to be found on Tae Bo workouts, and if you really enjoy kickboxing, I have a few workouts I can suggest. I love Taebo Fat Blasting Cardio. They use the Billy Bands for a part of this workout, but you can get by with hand weights, or weighted gloves, and if you really want more intensity, you can add on ankle weights. Also the Elite Fat Blasting Cardio is pretty good. I used to be a Tae bo Junkie, and I have just about every tae bo workout, but for some reason, I have been into other workouts lately, and now I rarely do Tae Bo. I love Powerstrike kickboxing workouts too. Have you ever tried any of the Powerstrikes?