Regarding the question of maintenance on your NAD and Adcom both are due for a recapping. A general rule of thumb is that capacitors have a life of between 20 an 30 years, regardless of how often the components were powered up. These parts have a significant effect on the sound quality and the sound of older gear declines gradually.
I just recapped my 24 year old Krell preamp and even though it was working fine and sounded good, the new capacitors make a noticeable improvement in the sound.
The B&W's are a little different story. They should probably be recapped too but for some reason capacitors seem to last longer in speakers. If you can pull out and disconnect the crossovers the cost to put in new caps may be pretty reasonable.
The big question is if you have an attachment to this gear and want to keep it. It will cost at least a couple hundred bucks to recap each piece of electronics and if you're ready to move on you could take that money and put it toward newer gear. If you still like this preamp and amp (they are both great sounding classic pieces) then the cheapest strategy would be to get the maintenance done and hang on to them. But from a purely financial perspective it will cost more to refurbish them than they are worth. The third strategy is to just keep running them until they fail which could take years.
It's been my experience that you could spend a lot of money and get just a marginal improvement in sound compared to a recapped NAD and Adcom. I moved from an Adcom GFA 555 to a Krell KSA 300S the the level of sonic difference was disturbingly low compared to the difference in cost.
I just recapped my 24 year old Krell preamp and even though it was working fine and sounded good, the new capacitors make a noticeable improvement in the sound.
The B&W's are a little different story. They should probably be recapped too but for some reason capacitors seem to last longer in speakers. If you can pull out and disconnect the crossovers the cost to put in new caps may be pretty reasonable.
The big question is if you have an attachment to this gear and want to keep it. It will cost at least a couple hundred bucks to recap each piece of electronics and if you're ready to move on you could take that money and put it toward newer gear. If you still like this preamp and amp (they are both great sounding classic pieces) then the cheapest strategy would be to get the maintenance done and hang on to them. But from a purely financial perspective it will cost more to refurbish them than they are worth. The third strategy is to just keep running them until they fail which could take years.
It's been my experience that you could spend a lot of money and get just a marginal improvement in sound compared to a recapped NAD and Adcom. I moved from an Adcom GFA 555 to a Krell KSA 300S the the level of sonic difference was disturbingly low compared to the difference in cost.