The Keg
Here is another recommendation for the Extended Denver Restaurant Week. Yes, the Keg is part of a chain, but it has several things going for it as part of the extended Restaurant Week.
First, it has a great location at the corner of 19th and Wyncoop, in the shadow of Coors Field. Next, it has quite a generous menu. Don't worry about visiting a restaurant with an otherwise fine selection, only to realize your choice for Restaurant Week is merely a chicken breast or a "petite filet". On the contrary, the Restaurant Week menu at The Keg includes salmon, filet minion, prime rib, and my favorite, their "baseball sirloin". Whether this is a referrence to the nearby home of the Colorado Rockies baseball team, or the size of the portion, I don't know. Perhaps it refers to both.
Furthermore, you have your choice of four appetizers and three deserts. I hate here for Restaurant Week in the past and frankly, I just don't see how you can go wrong.