Punching power is about leverage not completely about strength.
There are some seriously strong guys who can't throw a punch to save their lives. Genurally stringy slimmer guys hit harder.

By the sound of it you want to improve agilty the list of possible exercises is endless.

You can work on these things. Balance, coordination, speed, reflexes, and strength. All "anaerobic" without oxygen exercises.

Watch the beginning of this clip. The shadow boxing Mike does is well worth a try and a target to aim for.
Find out just how good you really are. LMAO

http://youtube.com/watch?v=xjzceds2qTo