I bought the whole series and it was a mistake. I've only used the three-day split (GSBSB, GSCT, GSL), Core Max, and Low Max seriously but, now that I get my cardio and all my lower body work strictly from Cardio Coach I don't even use GSL or LM anymore (though I can see re-integrating them in the future, particularly GSL). I can't say enough about the usefulness of CoreMax, though. When I haven't worked my core in awhile my back aches. Most people lean toward split style (3 day or 4 day) heavy weight workouts OR circuit. If you're into one you probably have no use for the other. Personally, I'm a weights girl so I have no need for Muscle Max and IMAX3 is a seriously high-impact cardio routine (for cheerleaders, I always say, and I'm way past cheerleader age). And I think kickboxing is a real drag. HOWEVER, fitness is a very individual thing. Lots of women love high impact cardio with loads of plyos and plenty of posters here adore kickboxing (though most seem to prefer Kick, Punch, Crunch over KickMax, I've noticed). It helps if you know what you like and what results you're after. Otherwise, you'll quickly find out why they call those dvd covers DUST jackets.