As Wayne mentioned, the ICE's haven't been to Kimber yet for a cryo'ing.
The ULTRA Bubba ICE (UBI) outperforms the CNU in terms of a little bit more open & a little cleaner sound. I didn't have both in my setup for too long to do more a/b testing. I do like the NextGen's performancewise a bit better than the Eichmann's. And I'm sure Wayne could put the difference between the two connectors into words better than I can (as I've heard him explain the differences quite well before).
Granted, a UBI digital isn't cheap. But most of the cost in that is in the 2 silver Slipstream Bybees. Go with the copper Slipstream Bybees and save a good deal. Or, maybe just go with a single copper Bybee, and Silver NextGen RCA's. There's many ways to have an ICE built (copper or silver NextGen's, copper or silver Bybees, and one or two Bybees), and they're all going to perform damn nicely. I think it all just depends on where the point of diminishing returns kicks in for you. For my boss, he wanted the best. So I had Wayne build me the best for him. And that's why there's a UBI option.