Speaker Cables : Moderate priced

Highly recommend Mogami as a primary cable.  My experience is they dont' subtract anything, while high-end speakers rely on some subtraction to create more imaging or detail.  Markertek has both single and quad types.

I would have a careful look at DHLabs cables. These are my goto budget cables and interconnects. Many folks will recommend them, top notch, reasonable cost.

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.