Just to clarify, there is a 20-minute bonus segment on Cardio Supersets (also on the disk with Low Impact Challenge) that requires a step. It's my favorite part of the Low Impact Series and perhaps all of the Cathe workouts that I've done (admittedly a limited number).
Most of the weight training programs can be done in a small area. Butts and Guts takes some room for the walking lunges, but otherwise is fine too. As far as cardio goes if you have room for a step you can do pretty much all the step workouts. Drill max can take some space with its large variety of equipment and skips across the room, so you may not want to use that one. Cardio Kicks takes quite a bit of space. KPC does not and Kick Max is ok, too. Some of the disc work is too big for my carpeted area and traveling push ups are not conducive to a small area. I usually modify and just do regular push ups or jack push ups. Hope this helps,