I'll go along half way with the above post. As far as cables go, I've found that a quality (i.e. not fancy or expensive) generic 12 gauge speaker cable is more than adequate to transefer all the musical goodness your amp has to offer to your speakers.

It's the distance and space from your speakers to your ears that is more difficult to predict and that has a profound effect on what you hear. Positioning, and room acoustics, are the second most important thing in determining the overall sound of your system. The most important thing is the speakers themselves.

Now, nobody has ever doubted that speakers sound different. Why? Simply because that's a given and is accepted by everyone.

As far as cables go, if the differences were as obvious as speakers there would be no argument but, since a lot of these cable improvements/differences rely on what you want and expect to hear and, when the rubber meets the road they disappear like a smoke ring, the debate rages on.

Likewise for biwiring. Results are mixed. Some say no difference, ohers say "night and day" and not always for the better. That's your call but, in any case, I wouldn't drop a lot of money expiermenting on this.

A lot of this hobby is based on solid science but a lot more is faith based. It's wise to know your own self before getting into the deep water.

For more reading (which may lead to more thinking) you might want to explore http://www.audioholics.com This site offers fairly comprehensive FAQ's on these and many other subjects.