How about allot of theory;
http://sound.westhost.com/cables.htm
You might justify the cost of expensive cables if your speakers cost as much as a new BMW, if not then put the cash into speaker. Speakers are the only part of the system that make a sound. If you can hear a difference from speaker cables then you've changed the frequency response of the system. If you like the change then that's great. I prefer to let the speakers "color" the sound of my system not the electronics. Some people like the sound of tubes with their 1-3% distortion but that's not accurate reproduction which is my goal.
As Gonk wrote, it is a controversial subject. You cannot measure the differences in cable in most cases.
Only esoteric cable manufacture that actually publish specs is Kimble Kable. The 4pr is as cheap as Monster cable. The specs are available online. Audioquest has a convincing line of BS but no specs, wonder why? You might consider the Canare star twist, very inexpensive. Twisting your own wire is easy and will get you within 99.99% of those expensive wires. Braiding is better but more difficult. Both methods reduce inductance at the expense of increased capacitance.
The Outlaw interconnects look very good and are reasonably priced.