We purchased our first sts 2 seasons ago,,we had a 9600 and it is a huge improvement,,I believe that there is a tremendous difference between the 9660sts and the 9660 walker,,,I would go with the sts if I were you. Deere is coming out with a walker_tine separator next year ,,,,from europe. It is supposed to be comparable to the old tx series of NH. Hope this is some help