Rob, I don't think you are doing anything wrong. Like you say, whether you are bumping up the dB levels during the pink noise test, or after the fact and adjusting that specific channel, you are doing the same thing.
I think some of the older EP500's had a "wake up" circuit, not sure the newer models have this...I know my 350's have a switch for "always on" or "wake up" modes.
How long have you had your 500? The point is that you should "not" have to keep bumping up the levels to make sure the sub stays on. 75dB's calibration is plenty to accomplish this.
When you say it will not play, are you saying when you start playing music or movies it drops out all of a sudden, or say after the next day of it working it is not working the next time you turn on the system?
If powering the sub off/on fixes the problem in the short term, it sounds like to me there is a problem with the amp.
