Rsbeck's last post was spot-on: cables cannot add detail or, for that matter, character to what flows through them. Yes, you need to be aware of impedence, etc., but that's it. By all means, use nice and appropriate cables. However, more careful attention to other components -- primarily the amp and speakers -- will have a far greater impact.
And, yes, having said that, please re-read "bryanhod"'s comments -- aside from the juvenlie invective, it is based on absolutely nothing factual. He claims to have listened to hundreds and hundreds of cables. That's fine. This is a hobby for some people, and some people really get into it, there's a pride of ownership factor, and, of course, a significant placebo effect.
I know quite a EE's, have a graduate degree in physics, and know several amp designers, sound systems designers, producers, etc., quite well. I don't know of one who buys into 99% of this stuff or, for that matter, who spends good money on "high-end" cables. Unfortunately, the "trust your ears" dictum is very misleading, precisely due to issues of suggestion, pride, enthusiasm, etc. Psych 101.
I highly applaud manufacturers who stand up for what's right in this matter -- and this means some of the biggest guns in the business, such as ARC, Mac, etc.