20 Year Old Amplifiers compared to 2017

To answer your question indirectly. I had a completely refurbished, mint condition,  Krell KSA-250 amplifier, sold it 5 years ago. The single most stupid mistake in my HiFi journey towards Nirvana I have ever made. Regretted the decision ever since.

Anybody remember Halcro? They claimed to have the lowest distortion and best sounding amp in the world. Where are they now? Every new amp manufacturer makes the same claim! A lot of B.S. gets thrown around! And the prices keep rising! 

About 20 years ago, I had a Krell KSA-150 that sounded great, first powering a pair of BIC TPR-600s then a pair of B&W 801 Nautilus. I chose it over a Mark Levinson 23.5. Then I had the chance to hear an Ayre V-1, which to my ears sounded more musical. The V-1 was upgraded to a V-1x and then a V-1xe. Each upgrade was audible. Then after a progression of amps, I settled for awhile on a pair of Ayre MX-R Twenties. So, in theory, the MX-Rs should sound Significantly better than the 20 year old Krell. I wish I could directly compare the two.

I tend to agree with willemj (and Peter Walker of Quad). All well-designed amps with sufficiently low output impedance and operated below clipping will sound the same.These claims of superiority over rivals are mainly marketing hype!