I will give the LCD-X a couple more days of playtime to 'burn it in,' although I've never been a believer of that myth and I've never had any of my headphone change in sound over time. The only thing that changed over time was myself getting used to their sound. That won't be the case here because I'll be alternating it with the 560 as I compare and review them sometime down the line.
The amp can make a difference due to impedance mismatching, but this is a planar magnetic we're talking about. There is no impedance mismatching. I am a firm believer in EQ as well so giving 3-5 more db on the region from 2-4khz is no big deal at all. It's how I was able to love the HE-400 for the past two years.
It's highly possible that-- with regards to Audeze's inability to make consistent sounding products-- that I've gotten a duller sounding LCD-X than others have. Take a look at the two LCD-X's measured on IF and look at their raw uncompsenated frequency response charts. One has a midrange that measures completely flat on the raw chart (very much akin to the HE-400, which means very recessed in that region), while the other measures +7db or so at 3khz, which is more inline with what an Audeze LCD2 would sound like. Just so everybody knows, I've demo'd the LCD2 before and found it to have much more uppermidrange and much more flat throughout that area, and the LCD-XC I've demo'd recently had much more upper midrange and much more flat in that area as well.