I'd probably go with Supersets/Push Pull. It's quite different than any of Cathe's other weight workouts. The premixes are great (my personal fave is the double set Push Pull premix). It does use a stability ball, so you might want to factor that into your decision.
Pure Strength is a three day split strength workout(vs and endurance workout). Since you already ordered the Hardcore Series, which will also include a three day split gym style workout (focussed on strength I believe), I'd go with something a little different, namely PP/SS. I think you get more versatility with PP/SS.
Although, if you are like many of us, you'll end up with both eventually!
Have fun,
Shelbygirl