Re skin effect, following is a quotation from this paper, http://svconline.com/mag/avinstall_designer_cables_critical/, by Bill Whitlock of Jensen Transformers, who is a distinguished authority in relevant areas. See his bio here: http://www.jensen-transformers.com/execprof.html
Regards,
-- Al
Skin effect is another problem exaggerated by hype. As frequency increases, current flow in a wire tends to concentrate toward its outer surface, causing an increase in AC resistance. At 20 kHz, for example, skin depth is 0.018 inch (0.46 mm), where 63% of current flow is between the surface and this depth (see footnote 4 below). For line-level audio interconnects, the effect is absolutely inconsequential even if center conductor resistance doubles or triples, because it accounts for less than 0.01% of total circuit resistance anyway. For loudspeaker cable, there may be some measurable effects because total circuit impedance is lower, but we're still talking about increases in resistances that, if the wire gauge is properly chosen for reasonable losses, are negligible in the first place.
(footnote 4) Ralph Morrison, "Solving Interference Problems in Electronics," John Wiley & Sons, 1995, pp. 61-62.
Regards,
-- Al