Al, I agree that skin effect might be unimportant. I only stated the boundary since cable companies (AQ FAQ) claim it is important and make all sorts of expensive arrangements like flat woven tape or helical twist of multiple wires on round hollow core (my Acoustic Zen Satori). It is far fetched concept but they know more than I do. There were sound differences between cables I used that I couldn't explain.
Tighter twist doesn't hurt and makes often handling of the wire easier. My router happens to be 5GHz. Such frequencies, once enter the box can either find LC circuit to couple to, or some nonlinear element to mix on - even while "searching" for ground return path. In addition to mixing there is also rectification phenomenon where many decades lower bandwidth amplifier converts high frequency signal into very small level DC (because of uneven positive and negative slew rates) that becomes "audible" when offending signal is amplitude or frequency modulated. We're talking microscopic levels - but why even to allow this garbage to enter amplifier's box. Wires inside of my Rowland model 102 box have very tight twist:
http://www.gzhifi.com/uploads/userup/0809/052315454K9.jpgWhy audiophiles select thick gauges? I'd like to know. Perhaps to reduce inductance?