When seeking to acquire a good headphone system, how much science does the average consumer need to take into account? In my opinion, very little to none. Instead of obssessing over the latest ABX results, try as many headphones/amp/source combinations as you can afford and stick with the one that sounds best to you, regardless of what the latest "study" says, which may very well be superceded by next year.
Look at the numbers if you want, but they are never substitutes for listening for yourself. Trust the opinion of someone with lots of experience listening to and comparing lots of different equipment over many years or decades, rather than someone who just looks at the latest studies and automatically decrees what people should or should not be hearing.
My rule of thumb is: "Listen for yourself." Don't let a silly old ABX study determine what you listen to. ABX studies kept me from trying SACD, DVD-A, and BD for years, but when I finally switched over it was the best audio decision I ever made (aside from getting the right speakers/headphones).
Several people on this thread have called me crazy, but of course scientists are the ones who are repeatedly referred to as mad. (Who hasn't heard the phrase "mad scientist"?) To sane people, the Earth is our home, but from the technological/scientific point of view the Earth isn't home at all but an object, a "resource" to be used, manipulated, and exploited. This "scientific" attitude is indeed insane and will lead to disaster. It already has lead to disaster (nuclear arsenals that can destroy the world several times over, pollution, environmental degradation, the constant threat that scientists, who continue to play with fire by trying to rip the very fabric of existence apart, will blow up the entire planet), it's just that we aren't being honest with ourselves about it. Thanks to science and technology, we're well on our way to becoming the Death Star, and if that isn't insane nothing is.