I have a RRA stripped lower and would like to turn it into a varmint rifle. This is my first AR build and I would appreciate any recommendations for a kit or an upper and lower (parts) combination.

First thing is to get a match trigger. I like the RRA  but there are a lot of choices. Definitely go with a free float tube. I recommend a stainless barrel.

Do you want to build the upper from parts, or get a complete upper?  

And second, how serious do you want to go?  Do you want an all out 24" stainless bohemoth, or something a little more versatile.

White Oak Armament has some pretty nice stuff that has tempted me on more than one occasion.  They'd be a great source for a quality barrel.  (or I think they have complete uppers as well)

A good bolt, barrel, FF forearm, and trigger should be all the special stuff you need.  Everything else should be business as usual, pick what you like.

Gundraw