JBL from 60-70x are great speakers.
But according to my experience with Altec 604E from 60x, crossover parts update makes a huge difference. Despite my speakers sounding good with old original crossovers, the changing of capacitors and variable resistors improved the sound to a different level.
I measured old capacitors before the upgrade and their values were OK. But in any case, old electrolytic capacitors, and potentiometers are not good for transparency and dynamics.