Denf, I like the way you described the Nuforce Reference 9's performance in your system which left nothing to the imagination, well said! It is intertesting to view your photograph & notice these huge Martin Logan speakers towering over these small insignificant mono blocks that are deceptively powerful.
After owning a few digital amps, I also have to agree with you that they are unforgiving of any inferior component that is connected to them but will greatly enhance a high quality piece of gear, there is no question, they are definately a technology to be reckoned with.
Currently I am using a ARC Reference II MKII preamp connected to the PS Audio HCA-2 in balance mode, unbelivable sound but intend to give the Reference 9s a try in the near future. This was my primary reason for asking your opinion on these mono blocks & I appreciate your indepth response.