the idea is home "defense" not home "offense"... if some bad dude wants to enter my home uninvited then i would want to deter them from what they think they are going to do - not blow their head off in one shot while also taking out the neighbors cat and dog(although it has crossed my mind)
...one shot from a 12 or 20 would probably do it (anybody here ever fire these indoors?)... i would be more concerned about having enough loaded ammo, just in case something went bad... keep it light, simple, and utilize "wide patterns" at short distances...
good luck
cheers!