I've used Jupiter 28g 5N (%99.999 pure) silver wire, its really good stuff. Recently, I tried twisting 2 stands of that with one of the 26g 6N Copper wire, which turned out great. I used 20g magnet wire as the ground in the same geometry as the anti-cable ICs, and used Switchcraft RCA plugs.
http://www.partsconnexion.com/catalog/wire.htmlThe results are (IMO) better than anti-cable ICs, and bested some Zu and Vampire Coax based ICs as well as a standard twisted pair I made using the same materials.
I also have a set of Jupiter ICs, they are also really good. They use 8 strands of 28g copper in a litz-braided helix. More bass and warmth compared to the silver anti-cable type... the silver ICs are very accurate, clear, and preserve detail extremely well.
http://www.jupitercondenser.com/jupitercables.htmWhat is "best" will certainly change with personal tastes and the system they are used in. I really like the Jupiter cotton cable in my system, but in a friend's system the silver anti-cable clone was a better match.
I don't know about solid silver speaker cable ($$$$), but I really like the speaker cable I made out of 18g silver plated copper w/ teflon insulation (mil-spec wire) in a star quad. Its $.18/ft online, and the 80 ft I used cost about $15.