If you need something with more punch than a .45 you need a rifle. But that doesn't seem practical for your purposes. I suppose 10mm Auto could be an option.
I will note since it was mentioned early on that most NIJ lvl IIIA soft armor (the heaviest you can get before adding hard plates) is rated to stop up to .44 Mag, including commercially available 5.7x28 rounds so if you were considering that for its armor penetrating abilities I urge you to reconsider.
+1 on finding a new neighborhood to do bank withdrawals in btw. Are you banking at Mogadishu Federal Credit Union? I've never felt the need to have more than one 1911 with a spare mag.
Sgt. of Marines, 5th Award Expert Rifle, 237/250
Expert Pistol, 382/400. D Co, 4th CEB, Engineers UP!!
If you start a thread, be active in it. Don't leave us hanging.
OEF 2011 Sangin, Afg. Molon Labe