I used AR (Acoustic Research) Microflat speaker cable, which I painted to match the wall. But i think they stopped making it. I can't seem to find it anywhere.
Here is a comparable product that is available in
16 ft lengths for $18, or
100 ft. lengths for $89.50. 16 feet would be enough for two surrounds in a room with conventional ceiling height, because you only need it for the run from speaker down the wall to the baseboard where it can be connected to conventional speaker wire using
connectors.
You needn't worry about it being only 18 gauge. I have it connected to 12 gauge conventional wire, and with only a 6 ft. run up the wall, it has a negligible effect on the impedance of the entire run from receiver to speaker.
