I don't box but for legs I pretty much do a variety of squats, lunges, calf raises and box jumps. In the gym I use either kettle bells or a straight bar for lunges but at my last duty station I used to take the guys for a run until we got to a pretty good hill and we did lunges up and down the hill with some sprints and high knees mixed in. The run back was pretty painful after several trips up and down the hill. I've found mixing in box jumps with my leg days has been very benficial. I think you said you are doing deadlifts but if not I would definately add them. A strong back and legs is the foundation for just about everyting you do. You do not need to go real heavy for deadlift either. 185 pounds at 4 sets of 10-15 reps is the most I currently do and when I am working a circuit I go down to 135 pounds. Kettlebell swings are also a good combo for legs and back.