The following assumes you know enough about electronics to solder and not work on gear that is plugged in, etc.
There is one bipolar cap per driver card that will cost about 20.00 each to replace with Black Gate caps, then 2 more polarized caps that will cost under $5.00 each. The resistors are mostly carbon, you could replace them with Dales from Mouser RN65's should do for most of them. One major improvement can be had by going to a Fred based bridge rectifier, you can buy them for about $20.00 from Michael Percy Audio. I would do the bridge first, the caps second, followed by the resistors. Next, mouser can get UF4007 diodes, these should be used to replace all the non-zener diodes. IF you are driving a pair of speakers that are very inefficent, next I would replace the PS caps.
If you decide to replace resistors or diodes other than the bridge rectifier, get hold of me for more specifics first!