For me, the updates that have had the biggest impacts to my preamp and amps were power cable for the preamp and speaker cable for the amps. The power cables for my amps also made a difference, but not at the same level as the speaker cables. I recently added spring isolation to my amps and that added more depth. I think it helps since I use tube amps.
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?