Foster_9 makes an excellent point. A comparison between a particular group of high quality DACs will likely yield different results in different systems.
Also, no mention has been made of what digital interface was used on the Weiss, which supports S/PDIF, AES/EBU, and Firewire. I assume that either S/PDIF or AES/EBU was used (probably AES/EBU), since some or all of the other DACs that were compared do not support Firewire.
Given that, some of the system-dependent variables and interactions that may affect the results include the risetime and falltime of the signal that is provided by the source component, which is almost never specified but can significantly affect jitter, in ways that have little predictability; the relationship between the length of the digital interconnect cable, signal risetimes and falltimes, and cable propagation velocity; the happenstance of how closely the characteristic impedance of the digital interconnect cable matches the impedances of the DAC and source component; the amount and the characteristics of digital noise that will be riding on the signal that is received from the source; the susceptibility of the DAC/source combination to ground loop-related noise; the ambient electrical noise environment; the jitter rejection capability of the DAC; the sensitivity of nearby components to digital noise that may be coupled from the DAC through the air or through the power wiring; and the data rate of the signal that is being conducted. And of course whether S/PDIF or AES/EBU is being used.
Regards,
-- Al