PCM lacks clocking? Did he go into detail? Without digging to far into it, PCM or Pulse Code Modulation has to be clocked somehow. Without PCM every single CD would be useless.
Found a few links discussing improvements to the CD. They may or not be relevant, but if you look at some of Werewolf's posts, he gives light to what maybe to look into.
I think one thing you have to remember is that people who spend thousands on DACs are going to have a bias against computers and less inexpensive DACs because they are under the impression cheap = poor quality and $$$ = good quality.
Links to reviews comparisons?