Best Overnight Trips in CO?

I always have Paul Magnanti’s site bookmarked, especially this page:

http://www.pmags.com/backpacking-loops-mags-favorites

Don’t neglect Great Sand Dunes NP&P.  Definitely interesting, and in a very different way than the rest of the state.  The park & preserve also includes a large fraction of the Sangre de Cristo mountain range as well, which is a very “thin” but high range giving outstanding views over the lowlands that surround it.  Lot’s of great little overnighters- mostly a ton of out and back hikes in the Sangres.  (When I get bored and need something fun to do for a day I hike Music Pass, though the road suffered from the flooding a couple of years back.  You really need 4WD now.)

EDIT- Crap, shoulda read your whole post.  Googlemaps says that Westcliffe is a 3hr 5min drive from Boulder, so you could probably only hit the northern end of the range in your time limit.