Really enjoyed reading this thread.
For me, Etymotic er4 is the most tonally accurate headphone (well in ears)
SR009 treble boost
SR007 pretty tonally balanced
HD800 treble boost (makes violins sound tin like)
LCDX/LCD3 (bass heavy) The former is better in terms of balance
HD600 pretty good
As a classically trained pianist, I also use my own recordings to gauge tonal accuracy and the piano is a very difficult instrument to reproduce. I find it infuriating that the TOTL headphones all fail to achieve tonal balance....