Best speaker cable for Focal Sopra 3

Good question for Jacques Mahul - he would probably point to a simple 12 awg cable.

I used Inakustik with mine to great success. They are tremendously well built cables. German made and it is easy to tell. High tech high quality materials. 

YMMV, but I am using Morrow SP6 speaker cables with my Focal Diablo Utopia III's and I like the way the speakers sound with them over the MIT S.3's that I was using. . .

One user i came across used Telluriumq Q blue diamond between his gryphon diablo 300 with good result.  The blue diamond supposedly has a laid back high and quite forgiving on slightly bright system.  I am using voodoo definition with my diablo 300 and sopra 2 seems pretty good as well.

It really depends on whether you are working to correct something about the sound that you do not like. If you love the sound then I strongly recommend Kubala Sosna cables. I believe the represent a baseline from which you can judge equipment by. Check em out. 

With my Naim Separates  NAC252 and NAP300 DR and Sopra3 - I was using transparent music wave super  and it was a tiny bit on the warmer side over all it was well balanced , switched to Chord Sarum T, noticed the presence of more details on the mids and highs but compensated on the Bass. Depending on what I am listening, it could sound Bright. I must say one hell of a detail coming out off Sopra 3.  At the same time I feel the fatigue  that was not there with Transparent.
I wish I didn't sell the Transparent cables.
My second set is a Tube mono blocks with Audiovalve Eclipse Tube pre amp, Transparent cable  added more warmth to already warm sounding  amp and preamp. Chord Sarum made it sound perfect for my ears.
For the Naim system I need to try out Audio quest Robin Hood  or the William tale.
Anyone has experience with Morrow audio cables. I have read good reviews.

Wireworld tends to be a good brand to consider with Focals.
They warm the speakers up, and improve the imaging.

However, you should listen for yourself. Some find the loss of detail not worth the improved image depth.