If you want to be op, change natures when you get to 7th street. I'd change Klang. You already have aron which is very good stell mon, Carvanha/Sharpedo would be good enough to your team.
May I ask, do you intend to change your whole team? I mean, you have metagross, gardevoir, noibat, bulbasaur on you box, astonishing mons. I don't know how acquainted you are with breeding, but some of them could use it, Absol for example can learn Play Rough, so you don't have two dark moves on it, giving more cover on your battles.