Josh at PVA gets my top vote. You can get a top shelf barrel from him with a barrel nut and it will be dandy in your action (need to have headspace gauges for any nut setup) and Josh makes good looking barrel nuts. Stand up guy and quality work. He also keeps action wrenches on the shelf if you don't already have them.
After that, I've had good results (and sometimes what I want is on the shelf) with James Kessler at Northland Shooters Supply. He's the guy for Criterion RemAge barrels. Keeps a decent variety on shelf in popular calibers, twists, tapers. Stocks a ton of headspace gauges. Second generation outfit and great guy to deal with.
In short, you can pick your poison.