If you're already issued a "concealment" type armor, and you feel it offers enough coverage, I'd stick with it and look at a plate carrier. More than likely you'll already have it on during duty. Plate carriers can be thrown into your trunk bag and ready to go with your extra kit; ammo, IFAK, extra lights, etc, for active shooter type call outs. A good plate carrier and a set of plates, if your agency doesn't issue them, will run you about the same as an entirely new set of soft armor and a new carrier, if needed.
If you're looking for a dedicated, external load bearing type set-up MSA Paraclete is pretty hard to beat but you'll pay for quality. I'd recommend a BALCS cut panel. Paraclete, Tactical Tailor and Eagle make good carriers for those. (Insert shameless plug here: I've got an Eagle BALCS carrier [no armor included] I listed in the trading post.) BALCS gives decent coverage and good mobility.
The NIJ just updated their armor standards too so you might be able to pick up an "old spec" set too. I haven't gotten into how much has changed, if at all, since my armor set is brand new.