That's a nice enough combination of drive units.
The HF1300 tweeter cuts off rapidly above 13kHz and a Coles supertweeter can be added on a separate filter without modifying the existing crossover.
If you are over the age of 45, aiming to extend the frequency range up to or beyond 20kHz is likely to be of limited value.
I doubt you'd gain any benefit from changing the B139.
The capacitors are probably in need of replacement, there are so many choices it would be best to look for what meets your needs.
The rear connection terminals are horrible and could be usefully upgraded.
If it was me, I'd just change the caps and terminals in order to retain a fair degree of originality on what is a collectible speaker.
It is impossible for anything digital to sound analogue, because it isn't analogue!