Unless there is a problem with your current cables. "upgrading" cables is more of a tweak to get the sound you are looking for. For me it has been mostly subtle changes. At times I can't even tell a difference. Most of my cables are not real high end. Only have a couple "expensive" cables.
Well, when I changed power cords on my HT subwoofers, that made a big impact. Weirdly both subs were now pulling more power at idle over the OEM cords. Not sure they really sounded "better" but they had a bit more punch.