Digging up an cold thread here, but I was curious if you've gotten around to building the mainline and comparing it with your C2A?
I have the C2A and use it with my ZMF Atrium, Verite Closed, and HD800S. I personally find the C2A to sound way better than it has any right to, but maybe there's some slight differences in tube selection, caps, and preferences?
I will say, I can see how one may want more less coloration and higher damping with the Atrium and HD800S. In that regard, I could assume the Mainline would be aligned with that preference.
While I enjoy all three on the C2A, the best synergy I've ever heard with it is the Verite Closed. It's just magic.
Would be interested in hearing more impressions.