I can't remember where I got this link http://sound.westhost.com/cables-p5.htm#Speakers, but it's a very thoughtful set of articles. Here he points out that psychological bias, and how you can demonstrate it on yourself. Namely, use an EQ mess up your system's frequency response, get used to it for a while, turn the system off, flatten the response, and you'll think the system now sounds awful (for 15 min or so).