Also keep in mind that all-season tires does not apply to the rockies. Get winter tires.
...or I could move my northern route further south by getting off I-70 West at Columbia, Mo. (friends @ Mizzou), thereby eliminating Denver, and driving across Mo. to I-44 South towards Okla. City and then taking I-40 West towards Albuquerque. Then, I could get a rental car in Albuquerque with winter tires and take a two-day run up to Durango. (It's probably cheaper than buying a full set of winter tires for my car, since we never have any real reason to use them here in the DC area.)
Actually, this might work, since I'd have an added opportunity to stop over at Wilson's Creek (Mo.) and maybe Pea Ridge (Ark.) for a day or two.