mhtoter1,
I was looking for a backhoe myself, for my JD 4200. JD makes a very expensive unit that uses neither the 3pt. nor a subframe, but mounts directly and quickly to the frame of the tractor ($6500). It greatly reduces the amount of forces absorbed by the tractor. Due to the high cost, I then looked at subframe mounts and 3pt. mounts, and the general consensus amongst most dealers was this: if I purchase a 3pt. backhoe, I should plan on having repairs done to the tractor in the future. Even with a subframe, I would be placing a tremendous (albeit, less) strain on my tractor, and risk some damage.
I decided that I'd rather pay the rental fee and use a rig that was built for excavating, and ensure that my JD lives to do almost every other chore for the next 25 years - these compact utilities are one of the best investments a person can make. Good luck, hess.