Step Works is my favorite non-interval workout from Cathe. If you do the whole thing on an 8" step, you'll be feeling pretty tired near the end. Do you have a DVD player, or VCR? If you have a DVD, you could get CTX and do Step Intervals (that has only 3 intervals so I don't consider it an 'interval workout') and All Step back to back. My favorites in order from toughest to not as tough but still challenging are (times indicated are without warm up and cool downs):
MIC 59 min.
Body Max Step & circuit segment 43 min. (the bpm kill me on this one!)
Circuit Max 42 min.
10-10-10 and All Step 47 min.
Step Works 40 min.
Step Int. & All Step 43 min.
Cardio Kicks 40 min.
Power Max 45 min.
Rhythmic Step 46 min.
Step Fit 42 min.
Step Jam 47 min.
Step Max 40 min.
Step Heat 35 min.
If you have the DVDs of the intensity series, it is very easy to add extra cardio. You can add the time saver step of C&W to the end of ME, PLB, or PUB. You can do Imax 2 int. 1-5 after PLB, then do Imax 2 int. 6-10 after PUB. You can also add the BC cardio and leg segments to the end of another workout to make it longer and more intense. If you have the tapes, then these suggestions don't really help.