I have barrels from Volquartsen, Adams & Bennett (Midway house brand, usually made by Green Mountain), and one from Hogue, made by who I have no idea. If there is an accuracy difference between them, it's overshadowed by a lot of other factors. The one that shoots best for me is the one that has the best scope on the rifle at the time. I have my suspicions that the Volquartsen might be inherently the most accurate, but it's always had just a fixed 6X scope on the gun, and I need a bit more to really get the point of aim consistent.
Before worrying about brand, my question would be, what is the rifle going to be used for? Bull barrels get heavy real quick. The standard Ruger 18.5" barrel weighs a scooch under 29 ounces. A 20" .920 barrel weighs 58 ounces, so it adds almost two pounds to the gun, fine if it's a range gun, not so much fun out in the woods.
Since you mention Butler Creek, their all steel barrels are fine, but they sell a "carbon fiber" barrel that is best avoided. Where a true carbon fiber barrel like the Volquartsen has a barrel that is tensioned by being tightened against a sleeve of carbon fiber, the Butler Creek version is simply a light barrel with a plastic sleeve textured to look like the real thing. It has a reputation of not shooting as well as a factory barrel.
What makes the aftermarket barrels more accurate is more a factor of their chambers that their diameters. They are cut to what is called a Bentz chamber.
If you look at a long rifle cartridge, there is a little step where the bullet goes from the rounded portion to the full diameter portion where the cannelures are. A sporting chamber is cut .775 long, which is just where that little step is. So when the round is in the chamber, the bullet is just short of the rifling. The nose of the bullet is in there, but it isn't touching, because it's under bore diameter.
A Bentz chamber is cut to about .690, which means that when a round is chambered, the bearing surface of the bullet is forced a little way into the rifling. This improves accuracy dramatically, but nothing comes for free. In a lot of cases, depending on the individual barrel and the type of ammo, you won't be able to extract unfired rounds. An aftermarket extractor like the Volquartsen helps a lot, but you may have to plan on shooting the gun to clear it.
http://www.rimfirecentral.com/forums/index.php
Rimfire Central has a forum topic just for barrels, so browsing around there should answer just about any question.
You should be able to do a bull barrel, stock, and trigger job for around $250, or about half that if you get a sporter barrel, reuse the stock, and do the trigger yourself.