Amp: Metric Halo ULN-8
 
compared with my Sennheiser HD800 and Ultrasone ED10 (the re600 really can be compared with some good full size headphones),
the RE-600 is not that revealing in the midrange and not that fast,
but still rich and punchy with clear midrange.
 
Stage:
HD800 has very good stage reproduction. (yes we all know that)
But when you listen to big orchestra (like Mahler, Wagner) you hear an exaggerated
instrument separation and a huge (... again exaggerated) room (not a fair comparison but : compared with my studio monitors PSI A21-m)
 
ED10 is for me the best in this department.
But RE-600 is also 3D! Stage is not big, but is there.
 
RE-600 has great Bass. I like it very much. i would say linear. not overemphasizing anything. 
Midrange : is not extremely detailed, but still there. I like it. you hear almost anything you need to hear when enjoying music.
Highs: are smooth. The smooth highs "could" be the reason that the RE-600 is a little slow.
ED10 has too much highs.
HD800 is bright, but is OKAY for me. I use it as a "tool".
 
High Mids : was annoying me. too much energy there. around 1.5-1.8khz maybe?