Refurbish vs New Amplifier?

Components drift over time. Most new parts have 5% tolerance. Everything has a sweet spot and at some point in time all components drift into (and out) this sweet spot. The first thing we do when we get a "sweet sounding" old amp is measure the components and document the values. If we do a one off build we use the schematic but with the "drift values" of that sweet old amp. You can get new components at a 1% tolerance to "dial it in" but they cost more. Heat and age take a toll on resistors-diodes and caps. I just recapped my Sonic Frontiers SFS-40 that's going up for sale. The dynamic range is back - it has serious punch. While I was in there I replaced the power transistor and now the bias is rock solid. Everything affects everything. If you love the circuit design it might be worth a going through. Capacitor design has come a long way in the last 20 years. A Rubycon 450v 10uf cap is smaller than the old design but most likely more robust. Transistors dry up as well. Room acoustics and one's hearing mechanism is probably more important. It never ends so don't worry :) 

cleeds is right. As a long term McIntosh owner, I have sent three vintage tuners back to the factory for complete overhauls. They were even able to replace front glass on a 40 year old MR77 tuner. If you have a good product and the manufacturer offers service, I would do it. 

Some good info here. An interesting discussion.
I have concluded that given the Krell has been in my system since I bought it new (way back when) the Krell factory guy was offering good advice.
If it ain't broke......

If I were buying this amp today (used) , I would have it "checked out" by a pro or buy from a dealer who bench tested before selling equipment.
The Krell to my "older ears" sounds as good as the day I bought it and is exhibiting no signs of any problems.