the KGSS is pretty solid.
i definitely preferred the KGSS/O2 over HEV90/O2. i suspect a BH or ES1 combo is better, but i think that just tells you how good the O2 is. and according to boze a blackgated KGSS takes it to another level - so modded, the amp may be close to the tubed ones. while the HE60 is in a sense a more enjoyable or engaging headphone, i don't quite consider it to be in the same class as the O2 or the HE90. it lacks the precision of the former and the elegance of the latter. although pairing it with the HEV90 definitely took it up a notch. the sound stage just opens up.
my rankings of the stats would look this way: (1) HE90/HEV90, (2) O2/KGSS, (3) HE60/HEV90, and with both Senns taking a step down in performance when paired with the KGSS. it would have been great to have a BH there or the ES1 running. that would have made things a bit more interesting.
maybe next time. ; )
