Body armor is a pretty subjective topic, IMO.
Budget, threat profile, situation, weight, etc all play a roll.
Ceramic can be fragile, steel can be heavy, poly can be thick... etc
It is my understanding that AR500 steel is generally avoided for rifle threats these days (not the company, the material).
They make "special threat" plates that offer some advantages in weight reduction but are not NIJ certified and are designed to stop specific rounds, no more no less.
For rifle threats I'd look at companies like
Hesco
Hoplite
Tencate
RMA
Midwest armor
Chase tactical
SKD
There is probably ones I am not thinking of.
Prices vary, of course, but you can get a Level IV kit (with carrier) for less than $500 in most cases. It's going to be heavy, though.
for IIIA, I think Safelife Defense is a good deal. the carrier has pockets for rifle plates if you need them.
They also make a Flexible Level IV vest that provides a lot of coverage. $$$ though.
I have been considering getting a set for some of the classes I teach.
I like the idea of concealable carriers that can scale up if needed.
Right now, I have my eye on the "Slickter" by Ferro Concepts.
I wanted an Esstac "Daeodon ASS" but they aren't making them right now.
Wearing the armor properly is important, too:
Now, I want to caveat the entire post with:
I've been looking into armor for a few years, but I don't own any (yet).
I have worn armor at matches (pretty fun), but that's the extent of my experience.
Me, in armor at a match (I know it's a touch low on my chest, but we didn't take the time to adjust it. Just wrapped the cummerbund around as best we could):