Amplifier's age

I agree with Jmcgrogan.
(Though tube equipment is my preference).
High quality serviceable amplifiers are always a very viable option.
You didn't forget to go around and kick all four little footers before you bought???

With ERbay it is very much a hit or miss game. In my experience it has more misses. If you see one for sale here or other audio fan websites it is amost always a hit. I you do buy from Ebay never (almost never) buy as is as seen and demand a right of return, if you think something is wrong, not if the seller thinks it works great. If he refuses your terms ignore that one and you will find another. To be fair you should pay shipping and listing fees.
If you got lots of money then just buy cheap and have it professionally refurbished.

I agree with jmcgrogan2,, Its not broke,sounds great, who cares whats better,how much better is the question, you would have to spend alot more now days to get better if you have a very good amp already!,, and on the bright side of things if the amp you have is very,very good, when you do buy another amp, keep the old one, a collecter may give you alot of money for it! cheers!

Most of my stereo equipment is 10-20 years old. The only components that I've had break on me were bought new, and thankfully under factory warranty. Getting them repaired in a timely manner is another story...

A 15-20 year old amp should be completely gone over and overhauled imo. Even if it sounds great, it will benefit and sound noticeably better afterward provided you find the right tech which is rare. If his heart's not in it, you likely won't notice anything. If it is, he will have chosen parts very specifically in order to improve and not just maintain it. Well worth the average $400.00 in that case.