Quado, in 1999 I replaced the Mallory brand, computer grade, large can electrolytic caps in a circa 1985 Threshold S/300 Series II. I stuck with the same brand and capacitance value although many prefer to enhance it. The change was easy and required only a screw driver and attention to their orientation. Sonically, the new caps may have imparted some smoothness but the real difference was slight if any. The main benefit was not worrying about it anymore. Although these big caps begin to degrade the day they're made it doesn't mean the sky is falling. Replace yours before they hit 20 years and you'll be OK fine.
On my amp, self adjusting has to do with regulating the bias of the output devices, which sets the amount of current flowing through them continuously as opposed to having them switch completely on and off.