I have re-wired many good speakers over the years, using many types of wire, from 5-9s silver, silver clad ofc copper, high purity copper, and dissected speaker cables from various mfrs. Results range from no change to excellent, but given the work involved I decided I would only do it in rare cases.
This year I bought a pair of Selah Audio Tempesta 3 way standmounts, which use very high resolution drivers, including RAAL ribbons, Accuton mids, and Scanspeak Illuminator woofers.
As I wrote in my earlier review of them, I'm very taken with the Selahs- they are extraordinary standmounts by any comparison, and by my standards one of the best speakers I've ever heard.
That said, I made a couple of minor crossover changes in consultation with Rick Craig at Selah, and noted that the internal wiring was pretty mediocre looking stranded copper wires. I started thinking about a re-wire and surveyed the options, and was impressed by the VH Audio (well known AA inmate Chris VenHaus) UniCrystal OCC (Ohno Continuous Cast) Copper wire with AirLok insulation. Here's Chris' description:
"Our OCC wire is meticulously drawn through special dies, dead soft annealed in an inert nitrogen atmosphere, and follows special handling protocols to minimize any surface marring, before the insulation process begins. Our unique AirLok insulation is a proprietary form of foamed/cellular Teflon that achieves a dielectric constant of less than 1.45! By comparison, the dielectric constant of solid Teflon is 2.1-2.2, and a perfect vacuum is 1.0. May be stripped by simply using your fingernails- so no nicking of the conductor with a wire stripper!"
The price was acceptable for such quality, so I bought 21 guage for the tweeters, 18 ga. for the mids, and paralleled 21 and 18 ga. for the woofers and main crossover feed.
As Chris states, it is very easy to strip; I did indeed do all the stripping using my fingernails. Nice.
So- how does it sound? In a word- marvelous, even stunning. I don't hear any difference in the bass, but the detail and focus in the mids and highs improved dramatically. Any trace of hash is gone, and I can hear into the soundstage further than ever before with ANY speaker I've ever heard. Smooth, refined, balanced. A beautiful result, more than I had expected or achieved from any other re-wire job I've done.
I paid around $150 for the wire, and I must say that in the context of the speakers' cost and overall quality, it is a dead bargain. The re-wire took about 6 hours, and I'm thrilled by the result. I'm not sure that I've ever heard better, more musical overall reproduction than what I'm getting now. For hi-rez copper hookup wire I can't imagine better results.
BTW, they sounded a tad dynamically constricted for the first 20-25 hours, but then opened up. All good now!
VHAudio website:
http://www.vhaudio.com/wire.html#vh18hookup 
