Perhaps #4's in a good compromise, I'm wondering if #2's wouldn't be even better, short of OOO buck.
I ain't compromising with anybody that invades my house. Birdshot might penetrate, buckshot will. Shoot buckshot. Our house shot shucker is a 20 gauge with but #3 buck in a 2 3/4" hull. But I have no doubt it'll ventilate you well across the living room.
edit: Oh, that being said, as a mere teenaged child suffering boredom I once or twice competed with my peers to see how big a pine sapling could be shot down with #8 shot. Seem to remember it'd chop a 3" to 4" trunk at about 6 feet. But it wudn't trying to kill me.
