In regards to seeing AZ cables selling for 1/2 retail, I have read on this site that there is an upgraded version of the Silver Reference interconnects, which would explain the good deals.
I cannot yet comment on the Acoustic Zen powercords, but I found that in my system, the Acoustic Zen interconnects and speaker cables were a better performer than my Harmonic Tech's. However, I think the HT's are really a great performer, expecially given its price -performance.
Several years ago, I went from mostly Audioquest and Synergistic Research cables: Diamond 3X, Sterling-Plus, Synergistc Designer Reference Power cords and Designer
Ref interconnects to all Harmonic Technology cables. I did this after extensive listening in my system using a friend's Harmonic Tech cables to compare to the AQ. The HT just worked better in my system contrasted to the AQ and Synergistics in most areas. (However, I do recall the AQ Sterling-Plus won in one area: they presented a warmer, sweeter midrange than the Pro-9's). I sold the AQ and went with all HT cables: Truthlinks were upgraded to Pro Silway II,then to the Magic. I used shotgun Pro9 speaker cables. I used these cables with an Audio Research VT100-MKII, LS25 all with NOS tubes, MG 1.6's, and B&W 805N/REL Stadium speaker combo.
Later, I had a chance to audition the Acoustic Zen Silver Reference interconnects and I thought the AZ's were quite a bit better than the Magic, especially in the air/ambience area, and presenting an improvement in soundstaging. Both the Magic and the Acoustic Zen had a great upper extension, but the AZ's upper range had a silky (almost wet sounding), airy quality that the Magic did not even hint at. (This characteristic may not be appealing to some.) I then tried the AZ Satori shotgun speaker cables which I thought bettered the shotgun HT Pro-9 cables by a good margin. Several aspects of the AZ Satori shotguns were immediately apparent: images were much more 3D, a larger soundstage, and the dynamics were quite a bit better.