You might look at Furez In-Wall Rated Speaker Cable. They make a 14awg x 4 wire cable (2 x 14awg = 11awg) or a 14awg x 2 wire cable. The wire is 99.997% OFHC C10100 Copper Construction (High Conductivity Oxygen Free Copper), in a 7 Bundle Advanced Rope Lay Design. The other unusual value with this cable is the foamed polyethylene insulation (FPE), which I have never seen at these prices.
I believe these come in either 25-foot lengths or a 500-foot spool. However, at AV Outlet, it appears that multiples of the 25-foot length ship as one continuous cable, which is what you need. Price-wise it would be hard to beat a star-quad, 11 awg OFHC copper cable at $0.75 or less per foot.