Yamaha A 500 Integrated Amp Modifications

Much much better coupling capacitors are available, as well power capacitors 4pole caps by Jensen,or Mundorf ,increase suzes by 50% in microfareds if room.are the best,as well  are better resistors, 
NEOTECH 6-9S copper Wiring   all connectors to  Copper Gold Type. Fuses and holders get rid of cheap steel fuses. Much better diodes, bridge rectifiers
Torroidal transformer  Piltron  Black double potted type . 
This is if it is worth it . This is probably over $ 1200, to do this depending on prices and labor st $75 an hour.

I forgot switches very important Elna Swiss Silver contacts  And get a much better  volume attenuator and nee on off switches.
 This is a true rebuild  for just a few areas would not do .a lot of cheap parts 
For sure in original model.  If it is something  you want forever.
Personally  if you could afford it by s nice used Through Reno hifi ,or online
The excellent Pass labs integrated amps .all depending on Loudspeaker demand.