I went through the same thought process about what component to upgrade. I'm my case I had a sense my QUAD 22L2 speakers were the weak link versus Monarchy amps, and N.E.W. P3 (Cary made) tube preamp.
A friend of a friend built me a pair of custom speakers. He used the drivers from the 8571 speaker. He modified the tweeter and built a much better crossover using Hovland caps, exotic inductors versus the stock crossover. Bottom line is that for less than $2k I brought the performance of my system up considerably. I don't think any amp, preamp swap running through the QUAD speakers would have offered the same performance improvement.
Best wishes!!!
A friend of a friend built me a pair of custom speakers. He used the drivers from the 8571 speaker. He modified the tweeter and built a much better crossover using Hovland caps, exotic inductors versus the stock crossover. Bottom line is that for less than $2k I brought the performance of my system up considerably. I don't think any amp, preamp swap running through the QUAD speakers would have offered the same performance improvement.
Best wishes!!!