It doesn't matter what screen is in the tractor if you're talking the GPS (name of the thread) 

Do you use a dealer RTK base station network for your signal? Or do you use a cell based system like Deere mRTK or Digifarm etc? If yes to any of those, you'd be paying usually per receiver (you have 7 of them) per year. It doesn't matter how many machines you have since you move those around through the year. It shouldn't cost any different this year as it did last year to run RTK on those 7 globes if that's what you did last year on all of them. 

Are the tractors brand new? Do they have integrated receivers? You can still run your regular 6000 on the cab if it has an integrated. And use them just like you were before.