I did something similar about 6 months ago.
You are correct; it's just two-conductor speaker wire terminated in a 1/8" mono mini plug. The hard part is soldering the wires to the two terminal on the plug. They are close together and it's very easy to short them against each other.
If you want to extend the wires, I wouldn't mess with trying to solder wires to a new 1/8 plug; I'd get speaker wire and solder it to the Klipsch-provided speaker wire. Basically, just make the wires longer by adding wire, instead of substituting your own.
I am a bit of an audiophile (on a budget) and I know all about trying to push lots of wattage thru skinny wires. I got on this train of thought that the Klipschs' amp was "suffering" b/c of the skinny wires, so I tried to make my own using 16-gauge wire and new miniplugs.
It was a bitch trying to solder the plugs, b'/c of the metal sleeve that screws down over the connections. I am handy with a soldering iron (15 years + experience) and had trouble. After a few shorted-out plugs, I just switched back to the stock ones. It sounds just fine.
I'd add wire to the existing wires; easier that way. Also, try to solder it and cover it with heat-shrink tubing; that is the most electrically and physically secure way.
