"Do you people listen to your equipment or to music?"
Both.
Many headphone amps sound different from one another. Some warmer, others, leaner. Some are more detailed than others. Each preferred by an individuals` taste.
Headphone amp?
I would like to add high quality headphones to my system, which consists of a Pass Labs XA30.8 and XP-20 preamp, and SoundScience Music Vault plus speakers. Do I need a headset amp or is there some other way to use say, a pair of HD800s phones? I could in a pinch plug in to my CD player but I doubt it would be as good my amp/preamp. What would the cognoscenti suggest?