supra sword excalibur speaker cable

Please forgive my candidness, but $2000 cables with $6000 dealer-priced speakers strikes me as a considerably unbalanced allocation. 

In my experience, speakers do get considerably more resolving than the Harbeth 30.1s, enough that even hardware store lamp cord will not constitute a bottleneck.

For example, either the Joseph Audio Pulsars and Philharmonic BMRs would yield greater improvement than any cable. 
 

As the OP stated, he is looking at a used pair of cables, so the figures you noted are a bit misleading.

I have used Supra cables for years and think they are neutral high value cables.  I have no idea how the Swords compare.  In the end, you really would never know unless you hear them in your system.  Here's a thought.  Offer the seller a nonrefundable rental fee of say $100 to audition the cables for a week that can be applied to the selling price if you buy them.

I have positive experience with Auditorium A23 speaker cables.

They are very neutral, which is exactly what I was looking for in my system.