The EF-6 is good with the LCD-X, but it is amazing with the LCD-XC. Things I hate about the EF-6 are that: (1) it is a big, ugly, heavy monster of an amp; and (3) the volume knob is a monstrosity. For $1600 the look and feel of the amp should be much better, but with regards to sound (at least with the LCD-XC), it is warm, smooth, and just perfect for the XCs.
EF-6 arriving tomorrow for a home trial. If it fails to impress I'll just stick with my trusty Conductor...or buy a Master 9