One "tier" don't make a heartache...or does it?

The top tier of bluegrass bands/artists is pretty clear to me, although each of us would probably question it at times. Regional and local would follow, I suppose. Is there something in between any of those rankings? Who determines what tier? Would a band move from one tier up or down to another?

What are your top picks in each tier? Let us hear it!

Pick away!