Just finished my Crack - 4 1/2 hours, everything worked the first time! it is dead silent with my senn 600's. Definitely the best sound I have had out of the 600's, I have always found the Senn's to be a bit lifeless with other sources. I am finding it to be a little muddled in the mid range area right now but I have only listened for 10 or 15 minutes, I'll have to give it some time.
I would also prefer a bit more definition in the upper ranges, maybe after spending some time, I'll go through the tube rolling posts and see what tubes might complement my listening preferences.
All in all a really fun project, kit was perfect and instructions absolutely spot on. It is a nice complement to my Stereomour. Gonna try to stay away from mods for awhile and just enjoy.