Here you go Diggs, you might also consider a shotgun also and there is the availability to use frangible ammunition also. They make it in all handgun calibers and shotgun. Frangible, or “soft,” rounds are designed to break apart when they hit walls or other hard surfaces to prevent ricochets during close-quarters combat. Here's a link for more info on the frangible ammo.
.40 Smith & Wesson Caliber:
One Shot Stopping Success: 71-96% (Actual)
Self Defense Rating: Best
Cor-Bon "Nosler" JHP 135 grains 96%
Federal JHP 155 grains 94%
Remington "Golden Saber" JHP 165 grains 94%
Federal "Hydra-Shok" JHP 155 grains 93%
Cor-Bon JHP 150 grains 92%
Winchester "Silvertip" JHP 155 grains 91%
Federal "Hydra-Shok" JHP 180 grains 89%
Cor-Bon +P JHP 180 grains 86%
Penetration can be expected to range from 10 to 12 inches.
The lighter bullet choices in this caliber, manufactured by any of the top five producers, have the edge over the heavier 180 grain loads. Recoil of the 135 to 155 grain rounds is also less.