Haven't heard the Carbon yet either (due to dropping out of the first run; haven't read a single bad word about how it sounds though). Whenever possible, I try to go balanced with every headphone and amp that supports it. I have a few pairs of balanced headphones, a balanced DAP (Pono), and a balanced amp I will continue using until the LC ships.
I believe Cavalli stated the LC was designed to mainly be used balanced. Hence some of the SE issues which are being improved for the second run.
How much difference we'll hear between SE and balanced depends on a few factors but, when done properly, there should definitely be an improvement. At this level, that's what its all about.
I'd say if you don't have any balanced headphones (and the necessary cables) and only plan to use SE, might as well wait for the Spark.