The best thing I've ever heard was a rebuilt Ampex from their glory days. Sorry, I don't remember the model.
I really think the the idler arm setup in reel to reels is the most important reason that they sound so good. Properly set up, idler arm equipment seems to give the best combination of speed control (belts don't do that well) and isolation (direct drive struggles with that issue).
Haven't really seriously looked at that theory above, but it seems to make sense.