re: Name a brewery that that is world-class, but under the radar and not well know...

In Nashville, Tailgate
-Love the fact that they constantly do small batches and have 25+ offerings everyday, but their absolute best is the Hot Chicken IPA. Never had anything like it.

In Georgia, Creature Comforts
-Not sure if they are under the radar anymore. While Terrapin still has my favorite beer, I love the versatility that Creature Comforts has. Favorite is probably the Automatic Pale Ale.

Ill also add Apocalypse Brew Works in Louisville.
-Very small place that I found by accident. I didnt like everything I tasted, but they have some radical ideas, and really hit on a few. The Double Tap, 2x Red IPA will put you on your arse.