I didn't have any idea that audio was as difficult to audition in Japan as you recount. I was under the impression that Japan was a "last bastion" of a nation of audiophiles.
To answer your question I don't know the Goldmund Nimesis but agree with your conclusion that 5K is an awful lot to shell out for a used amp that old. The fact that it was "overhauled" speaks to either of two obvious possibilities. It's performance was compromised by old capicitors or worse, and this represents a truly miserable liablity, or a true fanatic was maintaing the amp to the highest standards. The likleyhood of either is difficult to assertain with any degree of certainty at this distance. However, you cannot discount that there is a clear downside risk.
You might want to weigh this risk against the veracity of the percieved culture of great respect for venerable gear in your country. There appears to be a strong demand for golden age hifi in Japan such as the JBL signature series of loudspeakers for instance.
To answer your question I don't know the Goldmund Nimesis but agree with your conclusion that 5K is an awful lot to shell out for a used amp that old. The fact that it was "overhauled" speaks to either of two obvious possibilities. It's performance was compromised by old capicitors or worse, and this represents a truly miserable liablity, or a true fanatic was maintaing the amp to the highest standards. The likleyhood of either is difficult to assertain with any degree of certainty at this distance. However, you cannot discount that there is a clear downside risk.
You might want to weigh this risk against the veracity of the percieved culture of great respect for venerable gear in your country. There appears to be a strong demand for golden age hifi in Japan such as the JBL signature series of loudspeakers for instance.