I have a lot of old PV amps, and the main filter caps do have a limited life. I usually go 10,000 or 12,000uF. More capacitance yields better headroom. Since modern caps are generally smaller in size than the originals, one can go with higher value caps. I have replaced caps in Mark III, Mark IV bass amps, XR600, and M3000. All had nothing wrong with them other than filter caps.
FWIW, a bad filter cap in the XR600 caused DC to kill 6 old EV SRO speakers (not all at once.) It would intermittently spit DC which would freeze the speakers (overexcursion). Fine after the cap change.
FWIW, a bad filter cap in the XR600 caused DC to kill 6 old EV SRO speakers (not all at once.) It would intermittently spit DC which would freeze the speakers (overexcursion). Fine after the cap change.