If you really want muscle mass, then it's the Slow & Heavy series you want. But of the two series you are interested in, I think the Intensities are way better at muscle building and strength training than the Blast series. PUB and PLB have done great things for me to build strength and shape nice muscles. And the ME tape can shape them for you with its tough endurance style workout.
I love Step Blast as a fabulous and fun cardio workout, it's one of my fave Cathe's of all time, but I could live without Step Jump & Pump if I had to. Push/Pull is OK, but it really only builds muscle if you do two or even three sets of each exercise and really heavy up, which means repeating the video twice in one of the DVD premixes, or by hitting the rewind button. Supersets I have not tried, but it is more endurance oriented. I have not tried Legs & Glutes yet either because I love other Cathe lower body tapes a lot, like PLB and leaner Legs and PS legs, so I have not felt the need to try anything different yet. I haven't done KPC yet, but I will like it and do it a lot once I just try it, I'm a little scared of it to tell you the truth! But again it's a cardio thing, with some muscle endurance work thrown in due to the drills Cathe includes.
For muscle development, I would vvote Intenstities, PUB and PLB are just the thing: and S&H.
Clare