One of the things that you did not tell us is what for tractors you have. If you want ot go the integrated auto steer in JD you have to be newer then the 7x00 tractor to go with Greanstar the 8x00 tractors will work as that is the first ones that they used it on. That is why you will have to go with ag leacer or tremble. We went through that last year after we got our 1770 planter and wanted to auto steer our 7700.We went with Agleader because we could put in integrated auto steer also we run an R62 combine and greenstar will not work on that combine for yield mapping 

PS. If you do not want to go integrated auto steer and have a JD combine then greenstar will work.