Absolutely no need for high gain with the XC. You want to use as much of the volume as possible to avoid volume tracking errors. The XC is so efficient that high gain would require you to listen at a very low setting on the volume knob. With my LCD-2 rev2, through single ended output, I use high gain to get the dynamics going.
I listen to the XC through the balanced output at low gain and I only set the knob from 9:00 to 12:00 (a range of about 75-90 decibels through my XC) depending on the track and my mood. Any louder than that for prolonged periods and my ears become very fatigued, not to mention possible ear damage.