Hardcore Extreme was my first Hardcore DVD and I ended up buying all of them except IMAX 3 which I intend on getting. Even though you have IMAX 3 in full on Hardcore Extreme, it is extremely annoying for me to keep going back and forth through the DVD menu. It ruins the flow of the workout for me. Also, you don't get the premixes. You do get High Step Challenge cyles 1 through 3 on Extreme but I would up buying that one too because I wanted the other 2 cycles plus the ab routine which I liked. I love all of the Hardcore Series and I use them a lot. The Gym Styles are my favorite strength series. Core Max has 3 workouts plus 3 premixes. Some people don't care for Stretch Max but I love it, especially #1. Muscle Max is my favorite total body workout. Low Max is a great low impact workout which was a nice change from most of Cathe's high impact stuff. I really like the music and choreography in this one and it's a real calorie burner, plus you get the premixes. Kick Max is another one I didn't know if I'd need, but after getting it, I'm glad I did. I missed all of the warmup and combos which I love. You only get the high impact blasts, leg drills and stretch on Extreme.
For me, it was definitely worth it to get them all and I am glad I did. I am extremely happy with all of my Hardcore workouts.
Marcy