I live in HoCo. Tyler Firearms is my go to. Easy drive. Bought, consigned and done transfers with them. Great group of guys and my first stop.
Past experience. Some distant past:
Done business with 2a Sales and SCSG, both recommended.
A little farther out: Elite firearms, Atlantic Guns, United, all different. All good. Bought from all of them.
I wish I was closer to Hafer’s. They seem to have a little or a lot of everything. Bought and consigned with them.
Medusa are good folks when I spoke to them at a show but they are a little far for me.
ETA: Just wanted to be a little more clear in my recommendation so I edited a little. Tyler Firearms knows how to run a business. Never a hint of any attitude or issue. Very easy to work with. They have good prices and can order most things. Their online transfer feature is second to none. I would only go there but I like to browse other shops from time to time for older things that may have found their way into the pre owned cases.