The link to the soundstring cable looks like 3 conductor, which seems like a waste. There 2 conductor bulk cable is
http://www.soundstringcable.com/gen2/Bulk-Gamma-2-12-standard-speaker-cables.htm
Belden 12 gauge CL3 in-wall is a standard, non-exotic cable. Parts Express and Blue Jeans have it and you should be able to find it locally at an electric supply house. 10 gauge also available.
http://www.soundstringcable.com/gen2/Bulk-Gamma-2-12-standard-speaker-cables.htm
Belden 12 gauge CL3 in-wall is a standard, non-exotic cable. Parts Express and Blue Jeans have it and you should be able to find it locally at an electric supply house. 10 gauge also available.