I am a dissenting voice here. If you don't have the GS series, you MUST get it! Using GS and S&H in tandem will give you wonderful muscle development results.
I do not like endurance weight training (MM, PH, etc.). When I weight train, I want to focus specifically on individual muscle groups, and I don't like feeling "rushed". The endurance workouts just don't give me what I'm looking for in a weight training workout.
So, if you are like me and want to focus on individual muscle groups, get the GS series. It is my favorite!!! Actually, I think if you have the GS series, the Pyramids, and S&H, you have everything you need to mix and match some awesome weight training workouts. Get Power Hour for those weeks when you want to "take it easy" (I put the quotes around that because no Cathe workout is ever "easy") with your weight training.