this is a fun informative thread
there are numerous items listed by others, highly respected, experienced users, that i have tried myself in the past and actually liked a lot... while i moved on, these items certainly would not be on my ’top worst mistakes’ list
big thiels, muse amp, vac pa 100 (i had/still have the 4 chassis 90-c’s), nht 3/3's... of course every component, at any level of quality and cost, has strengths and weaknesses, but i think this just shows how varying personal tastes can be, how different specific use cases/applications are, how important synergy is in systems with mating components... fascinating stuff...