I got the Nixon Dackit which is the barebones unit. As Nixon has told me and just about everyone else, each of his DACs sound different, and the plus versions do not necessarily sound better.
As for a comparison, I used to own the CI Audio stuff and thought its great. But, my personal taste leans towards the Nixon DAC.
The Plus versions have tube or video buffers along with more blackgates and less panasonic caps. None have digital filter or analog stage, so one has to beware of the DAC's output being out of phase. I have absolutely no problem with phase in my system.
As for a comparison, I used to own the CI Audio stuff and thought its great. But, my personal taste leans towards the Nixon DAC.
The Plus versions have tube or video buffers along with more blackgates and less panasonic caps. None have digital filter or analog stage, so one has to beware of the DAC's output being out of phase. I have absolutely no problem with phase in my system.