By a coincindence I tried an old KORG DW-6000, probably from the 80's. Could anyone tell me the specs of this synth and their opinion/thoughts about it. Should I buy it just for fun??

Buy for fun? Sure, why not when you can get 'em so cheap.

6 voice
2 digital oscs with 8 waveforms selectable
24db/oct resonant analog filter
2 envs (ADBSSR)
Built in chorus
No velocity or aftertouch

see:
http://home5.swipnet.se/~w-57218/art/synth/dw6000_e.htm