I fully agree with Tomfuller on the rental car out of Denver. My experience is that car rentals in Denver are much higher than other cities.
I don't think I agree with him on the slot canyon in Arches. They just aren't the same narrow slot as other places in UT and I have even done canyoneering a couple of times in the park with a guide.

all things considered after all is said, I would skip Aspen .. other than to say you've been there and a t shirt that is all it is .. it is a long, at times slow drive over and thru the mountains to Aspen .. just hit I 70 out of Denver and head to Grand Junction and start the adventure .. plenty of pit stops along the way like Vail and Glenwood Springs .. have fun and be careful !!

You've got some great advice here and lots of different opinions. As has been mentioned Denver is very expensive for car rentals, last time I rented there it was $400 more for a 4wd there than I paid the next trip from Las Vegas for the same car, so do add that and a drop off fee into your money plans.

Consider doing a loop from Albuquerque with the baloon fest at one end or the other and consider doing the loop in either direction depending on availability of lodging and energy. The only outlier would be the Aspen area although you could include Grand Junction either before or after Arches/Canyonlands.

BTW, I'm in the Canyonlands is awesome, Goblin Valley is interesting but not great and Page area has some nice attractions school of thought.