The problem with weight lifting is that big bulky muscles have no use in boxing. If you are just using boxing to get into better cardio shape then go ahead with the body building things. But if you are wanting to compete and be the best you can at boxing then they wont help you in boxing. Do low weights with high reps. Choose a weight that you can curl/bench/(whatever else) for 15 times in 2 or 3 sets. This will help build muscular endurance, which is what you want with boxing.