Hook-up Wire: Duelund DCA16GA vs Neotech STDCT-16 vs Cardas 15.5 AWG

In the end, I decide to replace hook up wires in my 300B integrated. 
I was using Neotech Wire 22awg LEGENBURG Rectangular for many ears in this amplifier.
I exchanged it to Deuelund DCA20GA wire from RCA inputs to input select (50cm) and
Deuelund DCA16GA wire from input select to volume control (10cm).
For volume control I use constant Shinkoh 90K resistor shunted by DACT 100K step attenuator.
The sound changed dramatically.
Much more dynamic. Much more high frequency resolution and air.
Soundstge is bigger in all direction, better separation between instruments.
A tone of guitar strings, piano, violins is more real.
Legenburg wire added upper bass bloom that made sound more lush and warm.
But, with Duelund wire in my integrated, the sound of my system still has enough meat on bones. 
The impression - the bottleneck was removed from my system.
The next step is changing  Legenburg to Duelund wire in my DIY phonostage...

Why is Neotech stdct hook-up bad?

Neotech Wire 22awg LEGENBURG Rectangular is not bad wire at all! It has very lush, musical sound with very good midrange.
I just say, Duelunc Cu-Sn is much better. 

I am about:
https://www.hificollective.co.uk/catalog/stdct16-neotech-upocc-copper-wire-1903mm-teflon-p-8458.html

I don't have experience with multistrand Neotech wire.