Unless you are going to wear it daily as a added level of protection (not sure) I would suggest a plate carrier w/L4 plates or AR500 steel plates for a "Oh fuck kit". If it is meant to be worn daily, I would go L3A with a hard trauma plate. Keep in mind, generally you will replace soft armor ($700-$1k) every 5 years or so, and on the year for the carrier ($60-$100).