I was in unit 66 for the 3rd rifle last year. I probably saw close to 100 elk on opening morning in the Powderhorn Wilderness area. There were 5 or 6 decent bulls in the group...however, I don't know how much this helps you because the snow had probably pushed some of the elk down. I'm sorry I can't help you with the outfitters, as I only saw Indian Creek Outfitters and they had a pretty good location for late season elk. I saw a lot of elk in my 5 days of hunting in the south end of unit 66, so you'll probably see lots of elk, but I can't help you with an estimate of the quality of the elk or where they might be in September.
Best of luck,
Kurt