Additionally, when one listens more intently, like after purchasing new equipment, one is more likely to hear details missed in casual listening.
It's easy to prove to yourself. Take a track you know pretty well, and sit down with no distractions, and really concentrate on it. Try to place each instrument in the sound field, take notes (whether mental or actual) about what you're hearing. I'm sure you'll notice details you didn't hear before. And you didn't have to spend a dime (unless you're taking actual notes and have to cover the cost of paper).
