Tonyptony, the PCM63K (PCM1702) is a R2R ladder type of DAC. There is nothing unique about it. It was actually the first R2R type of DAC to achieve the highest precision in the industry by implementing the really expensive at that time Laser Trimming techology for the R2R resisitor ladder. Other than that, you can build PCM63 at home using some logic devices and it might even turn out better than PCM63, less the precision of laser trimming..:-)
Even the latest BB DACs still use R2R ladder with current output. If you really ask me, the patented "switched capacitor" DAC in the Crystal DACs is superior just because there are no currents flowing trough it. The dynamics and high frequency extension are unmatched. This is the reason for its superiority over all the rest.
Anyway, it is all hype. It is best to trust your ears! And believe me, who say we all hear different, according to me, is not true...:-)