The two I used after I got tired of the Reebok video were Keli Roberts' Ultimate Step and Kari Anderson's Fitness Formula. The Keli Roberts video has fairly simple choreography with some fun arm moves. There is a lunge section at the end that will help you build up to greater intensity. I don't remember much about the set, but it was "normal", not depressing. Fitness Formula is probably a little less intense but has slightly more complicated choreography and a pretty, airy set. I did this one this summer when I was recovering from an injury, and still found it fun. It also has a good ab workout at the end. Both instructors are very likeable and cue well, and Keli has a great Australian accent.
Another recommendation I've seen is for Kathy Smith's Step Workout, but I'm not familiar with it myself.
I actually started doing Cathe's step videos right after I got comfortable with these two. I started with PowerMax, even though the Wedding Video, Mega Step Blast, and Step Heat are usually recommended as first Cathe videos. (I didn't know this at the time!) I just put my step down one level from what I was using for Keli's and Kari's videos, and didn't have too much trouble except for the last section. So for me, these two videos were very successful as a "bridge" between the Reebok video and Cathe.
Good luck,
Audrey