If I were to replace the 15" BlueLine in my MAG with a 500W 15", what would that get me? If I were to hook up an ext. cab (210), what could I get out of that? Anyone have a similar setup?
If the new speaker doesn't have the same specs as the old speaker, it's a crapshoot. Chances are it will either have weak bottom end, or it will overextend and tear the cone. Cabinets are always designed to match the speaker specs. Adding another cab is a far better thing to do. But you're going to have to try it and listen. Both on stage and in the house.