I believe there are also 'connectors' for RCA wires that would work... they just look like a little 2-inch double sided RCA connection - connecting two seperate cables together.
However, I am not sure if this would be the cheapest method unless of course you have some spare RCA cables laying around.
If its just regular speaker wire, simply cut the two(?) wires, strip a bit off the end, and twist it together with new wire that you have bought - just tape each of the two off seperately making sure the copper inside doesn't touch the other.
Good luck
