I regret whenever posting on AC due to the large amount of inflexible "flat earth society" members...
Directionality for me is dependent on the geometry of construction and the asymmetry of any "add-ons" to the wire / cable...
Most important, as Paul Klipsch once said, "The quality of the build (& design) is more important than the quality of the parts"... you could have the best parts or wire in the world and if you don't know what you're doing, you'll have an "OK product", nothing exceptional...
I agree with a single dedicated line to avoid "ground loops"... in my two hi-fi rigs, I run separate dedicated 10 AWG, highly annealed, copper conductors, into cryogenically treated Hubbell Specification Grade receptacles... No complaints with the results whatsoever...
Merry Christmas & Happy New Year to all,
Pete