Sorry to hear about your troubles with the ep600.
Although it is always frustrating to go through problems with new equipment not functioning as designed (especially when it is not cheap) it sounds like Axiom is making a solid effort to make things right.
Neon has provided some good advice on calibration. I choose to run my sub about 5-6 db hot during most movies. I usually use the quick access to the sub level from my denon remote to bring it back down during music playback though.