Im guessing your asking about the "speaker" wire and not the 3 prong power cord,,, it does help to be specific.
If you are in fact asking about the speaker wire its very easy to extend and will not void your warrenty.
The speaker clips have release pins on them,, just push in the release pin and the clip comes right off,,,, get longer speaker wires and put the clips on those new longer speaker wires,,, Ive done it before and it takes just a few minutes and its very easy.
Just make sure to connect the correct clips to the correct wires, (poss and neg sides of the wires to possitive and neg sides of the clips).
As I recall, the instructions how to do it are also in the manual.