Well... regarding the last posting, that's not entirely true. There are some differences between for example the Nak PA 7 and the similarly specced Threshold S/300. Both use the STASIS-design made by Nelson Pass, but due to a different lay-out and different components, for example the power-transistors, there is a difference in sound. To my ears, the Threshold sounds better, but the Nak is a great sounding amp.
As for the capacitors: a very rough comparison is that they act as batteries, only faster responding. They separate the electronics from slight changes in the incoming elektricity by storing energy, releasing this energy as the music/volume demands more power form the amp. When caps get older, they lose the ability to store and release energy. I had my Threshold revised a couple of months ago. The technician measured all components, and they were still on, or even over spec. Changing the big capacitors will cost around 250 dollars. So it's up to you to decide if you think the amp is worth it. Also, caps tend to get older quicker when the amp gets hotter, so caps in a Class A amp wil lose their capacity quicker.
