I agree, you will love the high step, it is worth every penny.  I was using the firm box too until last week. I got my high step in 3 days and my firm box went promptly in the garbage!!! I "highly" suggest getting one.  It has better grip on the platform and is more adjustable.  The price is fair too.  If you get the platform with 5 risers you get a Cathe DVD too.  It is a beginners/intermediate workout, but is great for light days or when you don't have a lot of time.  It can also be used with other workouts when you want to do a bit more.
I'd love to hear if you get one and how you like it!