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

Synergistic Reseach Atmosphere Level 4 SC's.  The interesting thing is that the SC's I had before (Acoustic Zen Double Barrel Shotgun) were great, but the difference across all parameters when I changed over to the Level 4's was immediate and transformational.  I love the additional deep inner detail, transient speed, beautiful true high's without compromising warmth and ambience, lush palpable mids (including an incredible realism to the human voice), exacting and impactful bass and a sound stage that is deep and wide.  I have heard the Atmoshere Level 2's and they have the same incredilbe qualities for less, but I found going up in price gave me the justiable difference.  I could not be happier.

I have the Crystal Clear Audio Cable (Magnum Opus) 99.9999% (6N) Silver and made a huge difference in sound Quality.  http://www.crystalclearaudio.com

@sabai - Interconnects are pure silver with insulation. Connectors for interconnects have insulation, they’re KLEI pure Harmony, so they’re pure silver. I’d need insulation, though. Kids and pets abound in my house.

Sorry folks my link to Townshend Audio in my earlier post was not correct it should be: www.townshendaudio.com

Sorry for any issues caused.

'Jaw-dropping' is asking a lot of any improvement, as others have said. However, I have found that all the cables can tune a system to a really valuable degree. I used some home-made copper cables for a while that were virtually identical to Wireworld Polaris (old polaris). I also had QEC Silver 12 (which is actually copper) that was very, very slightly better than Nordost Purple Flars.. or perhaps a tiny bit better. However I purchased some Analysis Plus Oval 8 and they are wonderful; very easy-sounding and balanced top to bottom. Definitely in your price range used.