you dont need to be a cardio machine for this!! most of the p90x workouts get a good sweat going. The core synergistics is a good workout which always seems to get me, and the chest back days always pumped tired me out. Ab ripper x is great as well. the rest is all very manageable. You could be on the biggest loser and still do your best on these vids daily, just make sure your following a good diet and keep at it. Youll get better and better... and i think Tony even says that.
10 minute trainer is not that great.