Hi there! I'm a Firmie, too. I've been using my Firm Box at the moment. But I do plan on getting a Club Step. It's nice to have a step, but there are some workouts where you don't need one like Kick Punch and Crunch from the Blast Series. Nice Kickboxing Cardio there. And since you don't have BSS3, I'd suggest getting a real step. Even if you did have BSS3, I'd still suggest getting a real step. The Box is a bit iffy, in my opinion. I'm waiting for a replacement at this time.
Cathe uses a barbell, but I have been using dumbbells on the shoulders instead. It works just fine. I also have to modify some of the higher impact cardio to lower, but it's so easy to modify. You won't have trouble there if you need to come down a bit.
Some of the vids use a stability ball, but you can easily go to the floor or sit on the fanny lifter if you don't have one. It's nice for the extra intensity for the core, but the moves can be done without.
Now, if you love love love CA&WT with Emily and Standing Legs, try the High Step Training videos. I have the advanced one and it's like a fusion of those two Firm workouts with the intensity bumped up about 10 times. I especially recommend it for you since you can use your Fanny Lifter with it and don't need a long step at all. And the only other thing you'll need are your dumbbells.
Have fun!!