Dob, I just finished my NCores yesterday. They are clearly better than my UCD400 monoblocks and I loved my UCD400s.
The NCores are more transparent, bass is tighter and there is simply more information presented. Without a doubt instruments and voices are more nuanced and the soundstage appears more defined. In complex passages everything remains sorted our, not that it was congested with the UCDs, but the NCores are simply better.
I was afraid they were going to be analytical or sterile based on some reports I read, but not in my system. I built my UCDs unbalanced and the NCores balanced. My front-end is the PS Audio PerfectWave combo with the upgraded DAC so balanced seemed like the obvious choice.
I did use upgraded Furutech XLR and IEC parts, Cardas Patented binding posts and Neotech wire for my internal speaker connections. But I used the same combo in the UCD400s. The only difference in my setup is the NCores and a balanced configuration.
If I had to say how much better I think the NCores are using a percentage, I would just take a stab at it by saying the NCores are at least 20-30% better except the soundstage. My UCDs threw a huge soundstage and the NCores are at least even, just more defined and nuanced.
I know my UCDs improved over time and if the NCores improve they will exceed the UCDs by a rather large margin.