Gery, I'm using the Goertz copper MI-2 cables with their solid silver spades.
I've been using this cable for more than 10 years.
The rest of my system details are listed in the hyperlink under my user name.
Note that, due to their flat ribbon construction, the Goertz cables have unusually low inductance and high capacitance.
Klaus (along with many other amplifier manufacturers) would likely be cautious about use of this cable as the high capacitance can cause amplifiers to oscillate!
For this reason I use a Zobel network at the speaker end which damps the cable's resonant peak and restores normal phase behavior in the Mhz region - this article is a good reference for the issue:
http://sound.westhost.com/cable-z.htm.
While the Khartago runs cool and shows no
apparent misbehavior without the Zobel, it sounds better with it - better image focus/depth and perhaps even better treble quality.