I don't understand your problem. You need to give more info. It shounds like you are a newbie. If so have you learned to fly with a trainer yet. The engine choice is your preferance. If you like normal power then you listed the manufactures recommendation. If you like to overpower it, then you need to be concerned about the weight of the engine as well. I don't recommend that a newbie overpower an airplane, as they tend to be heavier and thus you will be more likely to stall and crash on approach or have more hard landings.