I have Totally Cool Step, and I love the music to it; Christi often also sings her cues to the music. I orderd The Fantastic Four from Ebay as well as Solid Gold Step, which may be a little foolish as I still haven't learned every step combo from TCS. I fid Christi's choreography to be much more complicated than Cathe's.
Cathe's later workouts, in my opinion, have much better music, and I like the music from Imax's 2 and 3, and Low Max. The Bon Jovi music in Imax 3 really gets me into the "zone," and I feel as if I could fly.