Hi there,
If you have the money and patience, yes it's worth it. The FZ600 in the 80s was similar in handling and performance to a 2-stroke TZR/350 YPVS. It was the 4-stroke hooligans bike. The frame was an award-winning race frame. The engine was a tuned XJ600 oil-cooled lump.
I remember in the 80s lots of TZR boys swapped them for the FZ600. What it lacks in straightline speed, it makes up for in the twisties!
If one was offered to me for the right money, I'd take it.
Whether it becomes a classic... I just don't know. However, a good rider on an FZ600, even by today's standards will lose, in the tight bends, many modern bikes.
I would class it as a classic Yam.