Your experience with Synergistic Research Foundation SX speaker cables?

I tried the SR Foundation XLRs and power cable as loaners from The Cable Co. lending library. At the time I had Acoustic Zen Matrix Ref II and Absolute Copper interconnects and Acoustic Zen Gargantua power cords. The SR power cord was an improvement in detail and speed but it wasn’t as refined overall. The XLRs didn’t match up to AZ they were slightly grainy and less natural sounding. I never tried the SR Foundation speaker cables. 
Now whatever I heard in my system with my ears doesn’t at all translate into what you will observe with these cables in your set up. Give it a try. But I think going up to next level SR Atmosphere may be a better choice. 

@tommylion $749 per 8ft pair retail? Not sure. 
But on a used market, may be. Acoustic Zen Satori or Hologram II, Kimber, Nordost, Cardas, Shunyata? If the performance of Acoustic Zen interconnects in comparison to Foundation is an indicator, I’d not pass up on a opportunity to try AZ speaker cables.