A 1,600' gravel driveway will take an awful lot of time to maintain with a Box Blade as your primary tool. I second MtnViewRanch that a Land Plane should be your choice if gravel driveway grading is your priority job.
I'm sure you two are 100% correct but I gotta watch my pockets. They don't go so deep. After reading here and what you and MtnViewRanch have said as well as others I'll probably save for a Land Plane for next spring. They do look like an excellent implement.