Fix it and sell it. The very best equipment should be good for 20-25 years. Cold equipment generally lasts longer than hot equipment. All other things being equal an AB amp will last longer than an A amp. But a very well constructed A amp may last a very long time. In line level stuff it is usually switches and pots that go first. As far as performance and durability go, technology moves on very fast. If you have the financial capability, redoing a system is a lot of fun and given the advances in digital technology one might approach the problem differently.
My own dictum is once a piece blows it is time to move on.
My own dictum is once a piece blows it is time to move on.