Vex, if you only have a day or two a week for training, I say sparring is the most important for sure.Your ultimate goal is to be a better boxer therefore you must get all the sparring in you can.If your pressed for time do pushups and crunches every morning when you wake up or before bed.Sparring is the most important tool to get better in the ring.You'll lose fat and condition your boxing muscles.Make sure your sparring partner is not overwhelming you though.As someone else said you don't want to get beat on all the time.Azz beatings won't make you better.Choose a sparring partner who's better than you, who won't hurt you at the same time.