My two cents would be that since NCore and UCD are closely related, and you know the UCD well, a comparison between those two would be the most valuable comparison for you.
Closely related?
According to what the master promises, and the first reviews here, Ncore is a pretty large improvement compared with UCD.
To me this means that Ncore might take its place among the better sounding amplifiers (DIY or not), which UCD did not achieve IMO.
Therefore I'd be more interested in comparisons with the better sounding amps.
Time will come that I will be able to do a comparison myself, I am not in the hunt. In the meantime there will be more reviews and user comments which will be very welcome to make the picture.