If you're actually serious, I'd go for some ceramic armor. It's way lighter although more expensive; AR500 steel armor is very cheap and will stop anything up to an armor piercing 30-06 (some might even stop that) but it's fucking HEAVY. Trust me... throw front and back (and side) plates in a plate carrier and try wearing that f'er all day... yeah, you'll very quickly tire of that.
There's a ton of companies that made body armor but I've heard
Spartan armor as being supposedly good quality (and I'm sure there's 9001 others but that's one I've seen recommended by knowledgeable people).