I agree that you can't go wrong no matter which workouts you choose. Volume 8 is all hills and is great on the elliptical, but don't underestimate the intensity of the shorter workouts! You will get out of them what you put into them, literally, because you gauge your effort according to your perceived exertion. I absolutely love 2, 4, 5, & 6, too. and even V1 has a place in my rotation. Some people even combine Vols 1 and 2. Sean dropped his prices to the lowest they've ever been, so if you can swing it, I'd get all of them!