I just got mine today. I love the sound quality of the d/a's, haven't tried the a/d's yet, nor have I tried syncing it to anything yet. I'm sure the clock contributes to the sound, but I understand that the stellar sound quality owes both to the choice of a/d d/a chip (Cirrus Logic CS-4272) and the method of filtering used by these converters:
from Sound on Sound:
"These particular converters use IIR (Infinite Impulse Response) filters instead of the more usual FIR (Finite Impulse Response) designs adopted by most competitors like AKM. Much research has been carried out to determine why many people hear an improvement in digital audio quality at 96kHz and higher sample rates compared with 44.1kHz, and many experts now seem to agree that it's not the extended frequency response that provides the audible improvements, but the gentler high-end filtering, resulting in better impulse response with less 'time smear' and cleaner transients."
full article:
http://www.soundonsound.com/sos/oct05/articles/echoaudiofire.htm?print=yes