I do business with several outstanding Brick and mortar gunshops: First and foremost, The guys at Trigger Time Gun Club in Longmont, Colorado are an Awesome bunch of great gun guys. They are humble and knowledgeable. They sell First Rate parts of a very wide variety. They are shooters and they not only have a great retail store, but they also have a nice indoor range and training opportunities. And Patrick Jones, the Gunsmith (gun magician) is as nice a guy as you'll meet and he builds one of the Best rifles you'll ever handle.
You should also take a look at Ark Tactical in Lakewood, Colorado. Noah, Roger and the guys are always helpful. They have a nice variety of guns and ancillary equipment. They also have a gunsmith on site.
Finally, Bower Tactical has everything for the discerning AR shooter. They have an extensive collection of parts to upgrade every component on your gun. Also, they have a tremendous amount of ancillary equipment.
Not a heavily AR shop, but Scotties Guns and Miliataria in Denver has the most eclectic variety of guns or any small shop in the city. Steve, the manager is a former Marine and current good guy as well. You can find classic guns, AR's and a host of other items to include lever actions and Mausers of all varieties. Steve also does CWP classes.
Just my $/02! Hope it helps someone here. Each of these guys also does transfers.