JD 620 disk info needed

[Slippy]

Looking for a disk. I think I would prefer the 3pt disk but don't know for sure. Anyone know anything about the JD 620 disk? Any idea what a good price is for one of these? Also, I have found a few 10 foot wheel disk that seem to be going for 5 to $600 in fair to good condition, how is that price? Anyone have a preference of one type over the other. Will be disking some rough areas in my hay fields and disk up some motocross track for my kids.
Thanks.