Splicing
Ok, well back in my day, I used lamp cord, which at 5 cents a foot was a great bargain. And while these speakers are cool and will do the trick nicely, I would guess there's no real benefit from buying anything fancy -- some plain speaker wire should do fine. So this is just to let you know I am probably not the right guy to answer. But what the heck, I will anyway.
If the current ends of your speaker wire are terminated, for example with RCA connectors or stereo mini-plugs, you can get extenders from places like Radio Shack. If they are terminated but you're feeling the urge to cut and splice, you can make it work, but it's probably a mess, since most likely the conductors are coaxial (a thin one on the middle, some insulation and a braided wire around the outside of the insulator). If they are round, they are probably like this; if they are flat with a split down the middle, they are speaker wire, even if perhaps very small gauge.
So if it's just simple speaker wire, which I am guessing they are not, you can do a couple of splices that will work fine. Get another piece from a store (or maybe steal from some appliance that doesn't need wire anymore
. A tried and true technique is, for both pieces: 1) cut, 2) split the two conductors, 3) strip 1/2" from the ends of the four wires, 4) twist the ends together, 5) electrical tape each connection, then 6) fold them flat and electrical tape over the whole thing. It's a work of art when complete that you'll be proud of for years to come. Or at least until it comes apart.
People who are not sloppy hackers like myself might 1) get a soldering iron and solder the strands together, or 2) get a crimpy/shrinky-dink connector (the technical term, I believe). First slip on the shrinky thingy, then slip the wires to be spliced into the metal crimp connector. Crimp with pliers or something, then slide a heat-shrink tube over the connection, heat with lighter, blowtorch, stove, magnifying glass, etc. until it shrinks nicely around the connection. Very neat.
In either case, do make sure to match up the polarity -- plus and minus should stay the same from end to end. Most speaker wire is either colored on one strand, or has a ridge on the insulation. If not, just flatten the wire out and make sure that you keep them lined up.
If the strands are really thin, like small headphones with mini-plug, think twice -- these can be thread wrapped with aluminum and can be a real pain. Get an extender in this case.
Or, leave the speakers close -- there's a reason the wires are not so long
Tom