What speaker cable made a major difference in the sound quality of your speakers??

Try Cabledyne. As much as I love the sound of Tempo Electric, the Cabledyne Silver Synergy SCs have the tightest focus regarding imaging I've heard in my system. Their a natural pairing with my new Kinki integrated and are very well made. 

They weren't as open or went as deep when I first replaced them but it took just a couple of days before they bettered the Tempo SCs in all respects. I think it's the shielding that helps them excel in their focusing and delivery. 

The best part is, they're a bargain for the price ($275/2.5 meters) and are designed by a former employee from Belden Wire & Cable. A sleeper product in this sea of overpriced cables.

All the best,
Nonoise

MM, that's the way Tempo Electric makes their speaker cables. I have a pair of high purity, soft annealed, solid core silver cables with oversized teflon jacketing and bare ends and it was the best SC when I had my Tonian Labs speakers. 

All the best,
Nonoise

Don't forget or underestimate the connectors. In my present system, and all through it's iterations, Zu Event Mk I gave me the best sound. Getting them at a bit more than half price went a long ways as well. But the best sound I've gotten from them was when I had Zu swap out the spades for the bananas on the amp end. 

The connection may have not been the best because of the five way binding posts but it was the change of metal that elevated the sound.  Simply going from copper to rhodium over a berylium core gave me a couple orders of magnitude more detail, separation, clarity, and focus.

Even the bass was better resolved and more defined as well as a better front to back soundstage due to the more pinpoint imaging. It makes me wonder if I had some of my first cables terminated that way, would I have every looked for more.

All the best,
Nonoise