Like other posters, I disagree that the PS series is intermediate. What makes any workout advanced is the weight that you use, the amount of rest that you take and the amount of effort you put in. All of these can be satisfied by the PS series. I used to do thr legs portion all the time. It was my standard leg workout and i grew with it as my first real entry into weight training. I still think it is efficient. I would alternate it with LL from the CTX series for variety.
However, I have to say, that now that I have the Gym Styles, these workouts are superior in my view. I like the music ofr the upper body sets very much, I ignore the music for the lower body because I am focussing so much on the exercises. The GS have a great deal of variety also and using the band and the ball, I think the burn and stress on the muscles is greater than that which PS can offer.
I no longer use the PS series. The S&H upper body work is my all time fave and it gets better results for me than the PS series can.
If you have the cash to burn, you could get the PS series. But, cash is always best saved for future Cathe workouts, I think.
You don't need the PS series. But, you could get it for the sake of variety.
Clare