It's not that amps have gotten that much better over time, it's the fact that these were (especially the Hafler) low priced amps. I built a DH200 from a kit in '78, did a few mods to it and cranked the bias way up toward class A. It runs a toasty warm and it is still in my daughter's system. Kind of dark sounding overall but still working after 26 years. On the other hand, I also owned a Threshold 400A back then which sounded wonderful and still does to this day.
