Before you bi-wire, consider this: The last length of wire in your speakers is probably a much smaller gauge than zip cord.

I had a problem with an Audax tweeter in my center channel, a DIY speaker, where the post pulled out when I disconnected it to finish the veneering. When I investigated the problem, by pulling apart the voice coil, I found the coil wire that connected to the post was thinner than a hair. I have RS 14ga running to the speaker, and some other 14ga inside, but the final wire size is so small that I didn't believe it could actually run current through it. (I was actually able to fix the thing though, to solder that wire to the lead I needed a magnifying glass. If you ever have a spare speaker, you should take it apart, pry open the drivers, just to see how it is really put together.)