Well the G36 makes sense since you already have a .45 and a slimmer one will be nice for IWB. With that being said, I'd try another caliber and size. Go with a G33 where you can shoot .357SIG, .40 and 9mm if needed. That plus the fact that it's very easy to carry and conceal gives it my vote. OK, I have one too so that's another reason.