I am in Johnny's camp with this one. Here is a quote from an article from ZED audio, see page 6:
http://www.zedaudiocorp.com/PDF/ZedManual-A.pdf
"Our personal opinion about “fancy” cables and exotic passive components may shock
some of you. I have never been able to hear the difference between a cheap or an
expensive RCA patch cord. My listening has been done using double blind A-B
comparisons. Electrons are not very clever things and they have no knowledge of the type
of material through which they are flowing at the speed of light (312,000 Km/second). The
ONLY reason we recommend high quality double shielded RCA patch cords in mobile
installations is to reject noise. My opinion about speaker cables is the same. As long as
the wire is thick enough, it’s construction makes no difference. As long as the amplifier is
stable into reactive loads with phase angles of up to 60 degrees, the amplifier is none the
wiser what type of speaker cable is used."