I am running the 518 flat @ 0db
Volume adjustment on the D6K's
via the MR.
Looking into I-Volume which seems to
be a Replay Gain device.This uses Sound Check
as a basis but improves control.
Will audition the results.

Roger

http://replaygain.hydrogenaudio.org/

518, 568.2, D6Ks, D6KC, iMac dual core, iTunes 10.1 (lossless), Apogee Duet, Kuro 500A, Logic Studio, Sound Devices 702.