Christy Sports, Colorado Ski&Golf, and BC Surf N Sport. The most knowledgeable guys are probably going to be BC and Christy's. Colorado Ski & Gold is hit or miss, but they do have a large selection. Stay away from REI and Sports Authority.
I did the tour of all the shops on the south side of Denver about two weeks ago and the kids working there were like 15 and talked like they were mentally handicapped.
My favorite shop in terms of employee knowledge was Eskimo. I didn't check out their boot selection though. They definitely seemed high-end only. I mean...they only stocked COLORADO made boards. That sort of limits the selection (in a pretty awesome way).
EDIT: 720 wasn't much better than BC in terms of employee knowledge but at least that place had adults working there and wasn't a Pacific Sunwear that happened to sell snowboards.