Any question answered...

^ That depends on how much power you're running to the speakers. For house usage lamp cable will be fine unless you're running it past power cables. But then again even with decent protected speaker/data cable you don't want to run it near power cable because of the noise it creates.

I read somewhere (AudioKarma?) that the standard cable used by movie theatres was 12 gauge lamp cord. Apparently even over long runs like that the losses were insignificant. This may no longer be the case, and I'm not sure how they dealt with power cable issues.