Wife and I traveling to Denver for a conference next week. Kinda foodies. Never been to area. One night free for a nice dinner.
Restaurant Kevin Taylor
Edge Restaurant and Bar
I have eaten at the first two and know the Palace Arms' reputation (can't speak to the last one). If you want classic fine dining, Kevin Taylor is very good and I'm sure the Palace Arms is too. Rioja is excellent and certainly fine dining, but it's more modern. So I think it depends on what type of experience you are looking for.
I'd take Edge off the list, it's a non-traditional steakhouse...but other than the massive wine/alcohol selection really is a steakhouse. For atmopshere I'd go to Kevin Taylor or Palace Arms. Palace Arms tasting menu is wonderful.