I suggest the Kevin Taylor restaurant at the Denver Art Museum, Palettes. They offer a 3-course prix fixe lunch deal for $23 and have a good wine selection. http://www.ktrg.net/ We went in January and our party of four loved it.
we had an outstanding lunch at lola yesterday (sunday). They have a brunch... leading into a great live band and fabulous meal. Great mojitos and vibe... not sure if it is open every day for lunch, but I will hit it again very soon.