I share cooey-fever with many CGN'ers.
I would happily trade my 600 for a Marlin Xt, Savage MkII, or Norinco ns-522...just sayin'.
The Cooeys I have owned were certainly accurate enough for my kind of fun. These were "utilitarian" rifles of their day. Affordable and robust. Lots about them to love for sure.
I find it easy to believe that any of the 3 you've listed would bring accuracy to a higher level. Newer isn't always better, but you can't tell if your next Cooey was stored warm n' dry, or at the bottom of the Atlantic.