Hi,
Use #12 or #14-gauge copper wire--good, generic cable (Radio Shack is fine) or the bulk cable from Monster if you want. Nor do the cables to different channels have to be of equal length. Use only as much cable as you require (unless you're anticipating moving the speaker further away). If the cable run is only a few feet or a metre, you can use thinner cable, 16 gauge for example.
Come, come, BBIBH; cables present a "complex load" to Bell Canada or Verizon when they are running hundreds of miles of cable. Linking the speaker to your amplifier the length of a living room is NOT a complex load. The speaker is the complex load, not the cable!
The only requirement of cables is to keep resistance low over longer cable runs, and that is accomplished with thick copper cable.
Regards,
