Upgrade Speaker Cables or Interconnects

If possible, run a dedicated 20 amp, 10-12 gauge electric power line(s) to your gear. I hired it done for $350. Then address your room reflections
with acoustic treatment. Glass and Hard surfaces make for crap
sound. Do not spend 10 cents on any cable or ICs until these are done.
Look out for ambient room noise intrusions also. Noisy refrigerator,
humming lights, etc. Your gear is well done so now address the other 1/2 of the equation. 

As you're looking for better sound , and all your gear "stands" on the electric power my suggestion is to not dismiss the quality of your duplex wall outlet . It was one of the LAST things I replaced , yet had the highest performance/ cost ratio .
 After a lengthy search I chose the cruzeFIRST Audio Maestro outlet . It offered quieter backgrounds and enhanced micro- and macro-dynamics with clarity and no editorializing . More life .
Not the cable answer you wanted , but my experience of improvement .
  I use only Analysis Plus audio cables , homemade power cords using Oyaide Black Mamba cables due to cost restraints . 

+1 @gadios20 amp circuits should be done first... save you years of chasing bass.

Lots of talk on here about power, and I concur. I have addressed this element of my system via a Goal Zero lead-acid battery generator. This generates are perfect, noise-free 60-hz sine wave. It has dropped the noise floor in my system significantly, and I didn't even think the concept of a "noise floor" was relevant in my system. Boy was I wrong.

Lots of good points made above that you should keep in mind going forward.  But just to stick to your original question, my experience is that speaker cables become more important as speaker efficiency drops.  My speakers have almost the same sensitivity and impedance as yours (i.e. fairly efficient), and I tend to hear relatively little difference between speaker cables and much more with interconnects.  As always with wires, YMMV.  FWIW, and best of luck in your search.