I owned the 665vxi (the older brother to the 655) for quite a while, but threw it into the trash a few years ago. The amp ran hot by design, and the parts kept popping in the heat and humidity, and took out my speakers one time. HK vintage amps are usually dicey, I would stay away.
The 665 cost me 11K on the used market in Mumbai, in reasonable condition. I would think a reasonable price for a 20 year old, 60 watt amp is about 8K, not more. I recently picked up a much more recent Sony ES amp for 8.5K and had an opportunity to pick up a Luxman (which would be a little older than the HK) for about 6.5K.
If you are keen on buying used, look for NAD, Luxman or Sansui, there are chances of them surviving over 20 years. Very few other pieces of hardware do.
