if you are not happy with your system's sound, no cable is going to fix that.
On the other hand, if you love the sound of your setup, a good cable might make it even better. though it also might screw it up
Elizabeth, you nailed my thoughts exactly. I have used a lot of different cables but none that I would consider to approach the impact of upgrading/changing components or speakers. I do perceive differences between types of cables based on materials and geometry, but of the better made cables I have used (including cables I have made) there have been only a few that I couldn't live with. OTOH, there have been speakers, amps, preamps and sources that I couldn't stand to have in my system. Therefore, in the hierarchy of things, it is my experience to first select and match components and speakers that meet one's listening preferences, suitably position them in a reasonably sized and damped room, provide good power (dedicated lines), deal with vibrations, and then finally consider cables when you feel the need to play around with stuff.