I have no idea whether one can hear jitter?
I bought a HiFace two and using it in the following set up: JRiver > Wasapi > HiFace 2 > V800 > V200.
The results are stunning, Soundstage has increased especially perception of depth, the transparency and also the improvements in bass is awe-inspiring! What a great little piece of kit!
I can also confirm your results with the gear in my signature. I think the only built-in USB modules that are better are only included in significantly more expensive DACs. The HiFace allows a significant offset in costs when using a excellent DAC that didn't engineer the crap out of its USB input. Another benefit is that it's very flexible with changes in equipment. I also personally enjoy the freedom of not being chained to a USB DAC, Schiit and Yulong come to mind.
Edited by brunk - 6/30/12 at 12:50pm