If you hunt out of a tree stand most of the time, like me, then I think you would want to get as much KE into your arrow as you can.You have to keep the bow comfortable for you to shoot, otherwise your accuracy will suffer.If your current set up is about at your limit for "shoot ability" ,then you might want to get a small fixed blade head to shoot well for you.This should get you a pass through,as long as no large bones are hit.
I know that the Rocket Steelheads are some of the better penetrating mechanicals on the market right now,but your KE is still a bit low.Shooting from the ground,hitting nothing but rib cage, you would probably shoot through the deer.Now, put your self 20+ feet over head, and I think your better off with a little extra punch,especially with mech.heads.Remember, your goal for selecting a broadhead is finding the one that will leave the most blood on the ground,AND hit where your aiming.