I ordered XLO PRO 600 speaker cables from www.fatwyre.com on their recommendation. They were responding to my complaint about thinness
and treble harshness on some recordings on Magneplanar MMGs driven
by an NAD C340 (CD player: NAD 514).

I compared the XLO speaker cables to Monster Superflat Mini cables, with
the XLO 150 interconnects in place. (All cables were burned in.)
I did AB testing using two recordings with sharp treble content: Chopin's
Piano Concerto No. 2 - Allegro vivace (Martha Argerich; Montreal Symphony
Orchestra/Charles Dutoit; excerpt on April 99 Gramophone CD) and Mary
Chapin Carpenter, State of the Heart, track 3: Never Had It So Good.

This was not very scientific, i.e., not ABX. I could not be sure there was
a difference between the Monster and XLO speaker cables.

The XLOs look like audiophile cables, whereas the Monsters look like
something you'd pick up at your local hardware store. (They're white and
flat and would be good to run along a white baseboard.)

To paraphrase Jerry Seinfeld on another subject, I knew it was a
gamble going in.