I have to tell you folks, my Underwood modded 5900 is really starting to sound incredible! I still am trying to get my head around just how to use every feature of the 5900, but in two-channel, I am very impressed with the detail, the presence, and the enhanced reality of the sonic images I am hearing. Dan's tubed output stage sounds like something special to me, although it is the first tubed-output digital source that I have used.