Quad 988 / 989 reliability ??

You might want to try Sound Labs as an alternative. Comparing new production to new production, fewer problems. In the right model, better bass - the kind you are looking for.

Just to put comments in context I have had so-called 57s for over 25 years, I had 63 for 5 years. I found that these speakers were no more unreliable than cone speakers. For example I have a pair of broken Celestions that are no longer supported by the manufacturer or importer. All in all I think that the SLs are more robustly manufactured. Both the late Peter Walker and Roger West are brilliant designers but contemporary SLs are a tour de force that are properly engineered in many categories including reliability.