Ya, speaker drivers have improved vastly as well as digital. That NOS TDA1543 dac is easily outclassed by cheap dacs these days and belongs in the obsolete category.
I remember hearing a Bel Canto DAC 1 and then upgrading to a Bel Canto DAC 2 because I believed what was written in reviews... and when I heard them, I asked myself either I had tin ears or it was florid descriptive review and I bought into hype.
I say, it was a combination of both.
From the digital latest and greatest revelations from different sites and audio forums, you think there are epistemic discoveries every couple of months, which I do not think is true.
All I can say, I have a Rega Apollo 35th Anniversary Edition and a Exogal Comet DAC with the external PS... They both sound great, better than the Bel Cantos they have replaced. I haven't heard a DCS stack nor a Mula Mula DAC which seem to be getting raves...not that I have the money to get those SOTA DACs.