Round 6 I was in a tag called "Chu-Hi". I guess I wouldn't call it an alliance, but we were all friends at work in the same gal. Our only goal was to be above 1mil planet wise, we were no where near top 100 gal. That round was awsome.
That round sort of ties with 9.5 though, with ETY. The first round I thought of myself* as significant. And first time ending over 5mil that I can recall. \o/
If I had to choose solely off of alliance success, I would have to say round 12 with 1up. I had never been so far ahead of the universe, to where the only targets I had were mainly my own alliance.
Was a very exciting round though.
*Key word: Myself