Yes, but how they want their headphones to sound is not necessarily how we want our headphones to sound. :)
Since no two headphones sound exactly the same, it's also going to be difficult to find one that's similar to the HD650. So if the "HD650 sound" is the sound that's right for me, and only needs a little tweaking to become perfect, then I'm all for getting more out of my headphones. Of course, because the cables have such a marginal effect, it's essentially the last thing we're supposed to change in the system.
Say our favourite headphone "sound" is a number, 195. The HD650s are the closest to that number, 200. Then the amplifier turns that sound into 190. The source changes that to 194. And the cable change makes it an even 195. That's kind of what we should be looking for in our music. First, to find our "sound" and second, to find the gear that lets us produce that sound. It's a little random, but hopefully you get what I mean. :)