What would be a good midway point for my drive?

"Colorado springs, Colorado" or "Pueblo, Colorado" would be a good mid-point for your trip if your plan is to travel west on I 8O and I 76, then I 25 south to I 40 west and I 17 south. However, I believe that my preference would be to divide the trip into a 3 day drive. So, I might stop at Julesburg, Colorado (517 miles), Las Vegas, New Mexico (511 miles), and arrive in Phoenix (539 miles).