Analog circuits are a mature technology, so I'm not surprised that a quality 20 or 30 year old amp can sound plenty good. After all, our ears are not improving, we're still using the model '1' ear system.

It is unfortunate, if true, that analog designs are actually getting worse from neglect though.

The only reason I 'retired' my Hafler/Carver etc. 2 channel system was to take advantage of x.1 formats. It still sounds fine on 2 channel stuff.