To my ears, I would have to say that going from stock power cords to a nice one like the Audience Power Chord, or one of Morrow's line on the power amp made an audible difference in the tightness and presence of the bass. Speaker cables made a difference as well, audible but subtle, more in the high end of the treble. For me, IC's made the smallest difference. But YMMV, since I don't have "golden ears" anymore, unlike some of you folks . . .
What makes the biggest difference in sound quality?
When making changes or adding things to your system, what makes the bigger difference in sound quality on preamp‘s and power amps? Interconnects, speaker cables, power cords, or fuses?