IMO LCD-2 eats up a lot of power. The rig I built for the HE-500 actually benefits the LCD-2 as well. Which was kind of unexpected and surprising. I think when people say the LCD-2 is easy to drive. What is happening is that it's easy to get the LCD-2 to sound "okay" or "good". On speaker amps the LCD-2 sounds better. There is just a ease and finesse about it. No matter how complex the passage of music it doesn't feel like it's running out of steam but punches hard and fast through all the details. There is no strain. As for volume matching, it's very close to the HE-500, almost the same depending on the amp.
I think the same principle applies to the HE-500. It's pretty easy to get them to sound good. But for them to shine or get optimal it takes a little more.