I try to touch on precisely this:
the following two comments are extracted from the LCD2 prologue and HE-6 prologue respective
In my 2010 review of my top 20 headphones, the LCD-2 was my runner-up choice, just behind the R10 bass-heavy model. At number 12, the LCD-2's noticeable difference in rank may deceive some into thinking that it has fallen out of favor with me. This is not the case. The reason for this is that since writing the original review in 2010, I have acquired an abundance of headphones and gear which gave way to several new front-ranking inclusions. The HE-6 and HD800 are the only two headphones on my current list to move in front of the LCD-2 from the previous list. The reason for this has to do with improved amplification. However, the most feasible reason for the LCD-2's fall in the ranking is the LCD-3; the LCD-3 essentially does everything the LCD-2 can do but with a greater sense of clarity and transparency. The two models sound quite a bit alike and perhaps I see less reason to give the LCD-2 head-time because of this.
In the time since writing my 20 Headphones Compared thread, I have acquired a Woo Audio 5. Hearing the HE-6 through the K1K output (which is designed to pump 8 watts per channel at 150 Ohms) has really opened my eyes to just how amazing the HE-6 really can be. Iron Dreamer's review of the HE-6/EF-6 combo has piqued my interest in the EF-6 amp, but I haven't yet pulled the trigger on purchasing it. The EF-6 is an amp specifically designed by the manufacturer to power the HE-6. I also have yet to hear the HE-6 paired with Ray Samuels Audio's Dark Star, which like the EF-6, was designed in order to meet the power requirements of the HE-6.
So how did the HE-6 and the HD800 flip flop?