I live in Denver. Fortunately The Music Room is about a 45-minute drive from where I live. They are a GREAT used gear resource (one of the biggest in the world). Here is the link to their current integrated used tube gear.
Interestingly, many of the gear suggestions in this thread are available used at The Music Room (PrimaLuna Evo 400, Rogers High Fidelity EHF-200 MKII, Rogue Audio Cronus Magnum III, Quicksilver Audio, Cary Audio SLI-80HS, and Coincident 34SE MKIII).