As a contrarian, I think you deserve an alternative response. I've owned and used many different kinds of speaker cable, and have done some "non-scientific" listening tests with friends using different speaker cables, and I found the Alpha-Core Goertz MI2 (copper) cables to be excellent. The MI2 cables have a very low impedance, and can cause some interface problems with certain amps (causing frequency oscillation in the amp), but that can be cured with the use of a Zobel circuit on each cable. For more info about Goertz cables, look into the A-gon archives -- there have been several very long threads about them, with some excellent input from our resident guru, Sean.
Rather like the guy who does the Remington shaver ads, I liked the Goertz so much I bought a bi-wired pair and have been extremely pleased with them. I'm not trying to "pimp" the Alpha-Core, but I think you owe it to yourself to audition them. You can get a set of cables from Alpha-Core for a money-back 30-day home trial, which is pretty hard to beat. (I agree that their ads with the woman using cables and interconnects as a halter-top are pretty stupid. The company's products deserve a much more intelligent marketing campaign.)