Zero latency still isn't going to fix jitter - that occurs at the DAC stage and there's nothing in the OS level that is going to fix it. If you are buffering the signal in memory whatsoever then you do not have a zero-latency system.
http://en.wikipedia.org/wiki/Digital_audio
http://en.wikipedia.org/wiki/Jitter
I'm not being super-picky here, these are digital audio basics that you are misunderstanding.
Here is some good reading from Wavelength Audio:
http://www.wavelengthaudio.com/usbdac.html
I've been using their Cosecant USB DAC for about a year now with great success.
http://en.wikipedia.org/wiki/Digital_audio
http://en.wikipedia.org/wiki/Jitter
I'm not being super-picky here, these are digital audio basics that you are misunderstanding.
Here is some good reading from Wavelength Audio:
http://www.wavelengthaudio.com/usbdac.html
I've been using their Cosecant USB DAC for about a year now with great success.