"but for a headphone user it's usually more simple than that, you always go with the lower gain and only ever change up when you can't get the headphone loud enough with the volume knob."
That's the part I already knew. Thanks for the rest. And before pulled the trigger I made sure to carefully scrutinize the aforementioned guy's webpage, along with the comments. It was eye-opening, to say the least and the conclusion I distilled was the one I quoted you for here. Yet, I'm still amazed how loud my HD800 gets even at low gain, I can't help it.