Speaker Cables : Moderate priced

Are these your current speaker cables? They have several desirable attributes such as the type of copper used, the gauge, and the dielectric material, i.e., 12AWG Long-Crystal Oxygen-Free Copper and PE dielectric. What do you expect to improve by switching to different speaker cables?  I doubt you would reliably hear a difference (much less an improvement) between your current cables and any of the suggestions here. I suspect there are other areas of your system where the $1,500 could have a greater (at least audible) impact on the sound of your system.

Back in November, you were interested in tinned copper in cotton speaker cables. Were you ever able to try a pair of those?

@mitch2 +1

that's a wise and solid advice. $1500 can be invested in a better source, preamp, etc. a much better ROI than the speaker cable upgrade 

For long runs consider making them from Furutech FS Alpha 36 from VH Audio.  I did this using gold plated Furutech spades and they sound very good.

Trust me on this one.  Go on the used market and seek out a nice pair of JPS Labs Superconductor 3 speaker cables.  No need to look any further up the JPS Labs line or anywhere else.  The Superconductor 3 speaker cables are some of the best speaker wire, IMHO, at anywhere near what they retailed for and way beyond (and they were definitely not cheap retail).  With the Superconductor 3, you won't have to go any further or spend more.  The Superconductor 3 could be your end-game speaker wire (they certainly are mine).  Over the past 12 years, I've upgraded every cable in my system, including my most recent cable upgrades, and my JPS Labs Superconductor 3 speaker cables were the only cables that I kept.    

+1 @kennymacc been using mine for well over a decade occasionally comparing to others w/no plans to change.