Only one word: UNCONCEIVABLE ! ! !
I have listen top of top mark levinson, chord, krell, mcintosh,convergent, but sigfried are the only one that make not the speakers sing, but the room sing: never listen something like this amplifier.
Probably with better tubes even better details, but I absolutly not suggest to roll tubes: a friend of mine did, but amplifier need to be repaired (were sigfried monoblocks)
In my opinion, no comparison with other ones I have ever listen. Before sigfried, I belived not possible a stereo system play music in this way.