The Middle Buster is a great, simple attachment. I am surprised they are not a bit more common. You can really heave up some earth with this. I have never used it for potatoes but I have use it to break sod and even dig a trench to refill with whatever I wanted to take the place of our terribly hard clay. And I did this all with the little 2305. I found that when you dial in just the right angle with the top link, you have enormous traction.
good luck
SI 2305
200cx, LX4, 5' grader blade, middlebuster, Landpride 60" RFM, Home made 3pt grass rake
good luck
SI 2305
200cx, LX4, 5' grader blade, middlebuster, Landpride 60" RFM, Home made 3pt grass rake