closer to 20 years old is my guess. The caps probably need to be replaced. I have not heard the Sonic Frontier Power 3's, but if you love them then why not fix them. You might also want to go and hear some modern tube amps. Get a better idea of what is currently available before you make a decision.
I had Avalon Indra speakers for a while and used an Audio Research Ref 110 to drive them. It was a very nice combination.