Here's a thread I started on the tiller I picked up. It's a 48" Hawkline tiller that I run on 1026R with 18 PTO HP. It is about the same width as my 1026R and a little extra width would be nice. In my soil type I can run it and power is not really an issue. Depending on your soil type a 60" model might work for you. Hope this helps!
I also have a John Deere 655 and according to the owner's manual, they say that a John Deere 550 tiller should work. It's a 48" tiller so I would say that any 48" tiller will work on your 655. I am looking for that 550 tiller for my yardwork.