I'm very much into (DIY) solid-core wires, in fact I use them exclusively throughout my setup as both power cables(16 awg copper, PE insulated, from the Danish equivalent to 'Home Depot'), speakers cables(Mundorf Silver/gold, ~16 awg, teflon insulated), IC and AES/EBU digital cable(Mundorf Silver/gold, ~24 awg, teflon insulated).
This may be a hotly debated topic, but as a very general rule I find solid-core wires sonically superior to multi-stranded alternatives. With both the copper and silver/gold(99%/1%) wires I've tried out the same positive characteristics shine through, although the Mundorf wires are more open and transparent(i.e. less restrained and more extended) - however also much more expensive, though worth it - than the Home Depot originated copper variants as speaker cables.
As (non-shielded) power cables though the copper wires sound very satisfying to me, and compare favorably to most anything, and much more expensive (multi-stranded) alternatives, particularly where shielded, I've tried. I'd be very interested to experiment with teflon insulated solid-core copper wires as power cables, being that many has mentioned PE is not the most ideal insulator.
With regard to the above claimed "impurities" found in the Home Depot-style solid-core copper wires, I'm sure there's nothing to it. I've read up on this, asked around, and at least here in Denmark the copper quality used in these cables is oxygen free and flat out excellent. There's nothing second grade about them. The typical yapping about from many within the hifi-community about these impurities is unfounded and exposes snobbery, if you ask me(and not least my ears). The problem is these cables are far too cheap to be considered with any serious interest by those who've been indoctrinated by the hierachy of "audiophile" cables and their (marketing proficient) manufacturers.
For speaker cable use I'd recommend trying out no thicker than 16 awg aolid-core copper wires, although very long lengths might benefit from a "beefier" wire.
