Ian's suggestion is the only one that would achieve meaningful results. As Peter pointed out and Ian confirmed, changes in factors such as slope, crossover frequency and relative woofer/tweeter levels in the crossover can definitely change the sound of a speaker, not necessarily for the better. If these products result in such changes, rather than simply substituting so-called "quality" components which don't change the crossover parameters, then there of course could be some noticeable change in the sound.

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Enjoy the music, not the equipment.