Power supply capacitors do indeed degrade, and if they fail (as they will) they can destroy your speakers. Since modern ones are often physically smaller, you may be able to fit modern ones with a higher capacity into the same case, for more dynamic headroom. Avoid audiophile caps: those from mainstream manufacturers are often better quality and cheaper.
Price is relevant here, because at least in Europe you can buy this amplifier’s modern successor, the Yamaha AS 501, for only about 350 euro. It is more powerful, measures better, and also has digital inputs. See here for a test of the previous model, the AS500 without the digital inputs but otherwise identical: http://www.avhub.com.au/product-reviews/hi-fi/yamaha-a-s500-amplifier-review-test-395710
It measures better than many audiophile amplifiers costing sometimes ten times more. In particular, frequency response under varying realistic load is stunning (within 0.05 dB). This is a perfect straight wire with gain. So don’t spend too much on refurbishing the old amplifier.
Price is relevant here, because at least in Europe you can buy this amplifier’s modern successor, the Yamaha AS 501, for only about 350 euro. It is more powerful, measures better, and also has digital inputs. See here for a test of the previous model, the AS500 without the digital inputs but otherwise identical: http://www.avhub.com.au/product-reviews/hi-fi/yamaha-a-s500-amplifier-review-test-395710
It measures better than many audiophile amplifiers costing sometimes ten times more. In particular, frequency response under varying realistic load is stunning (within 0.05 dB). This is a perfect straight wire with gain. So don’t spend too much on refurbishing the old amplifier.