Best lower options?

I'm a big fan of the Vz.58 short-stroke piston design which led me to the BRN-180. I'm optimistic that a Gen 3 will be released this year, so as somebody who doesn't own a BRN-180 upper at all, I want to put together a shopping list. -- A good forged lower, preferred folding stock, etc.

This will be my first AR15 build of any flavor, so I welcome recommendations.

Edit: I decided to go all out.