Wickenburg is worth a stop. There is an interesting Western museum in town and the unusual (for the area) Hassayampa River Preserve a few miles to the south on the road up from Phoenix.
The highway then heads through The Joshua Forest Parkway to another nice little town on the railway tracks, Kingman. There is a small but fascinating Route 66 museum and should you wish to break your journey for the night, this would be the place. Plenty of motels on the outskirts and the historic Hotel Brunswick in the centre of town. Earplugs are supplied!
From there it is about an hour to The Hoover Dam where you may get held up even if you decide not to stop. By staying the night you would get to the Dam at a reasonably early hour before it gets too busy.