If it's primarily for Weddings and similar events I would strongly suggest you at least look at selling the 17-55mm and buying the 24-70mm f/2.8L especially on a full frame camera it is a very nice all around lens and it will fit in with your current list of lenses very well too.

You could also consider selling the 70-300mm L and purchase the 70-200mm f/2.8L and the teleconverters as well.