I just thought it was worth mentioning that I thought I had a similar problem. The 100 is powerful enough to get things in the house rumbling along with it. Might be worth it to try it outside with nothing near to vibrate. Then again, it might not be this at all. I am not the only one who has had this happen though!!
Thanks, Greg. Actually, it's not a vibration, but kinda like as if you tapped the cone with your finger at the attack of the note. I've heard the sound before in other speakers where they were overpowered. It's not the sound of my nails either, nor do I notice it in the headphones. It just sounds purely like a speaker that isn't up to snuff to the power applied to it.
Can't find anything wrong with anything. Nothing loose. I did notice that the cab has no bracing inside from what I could see from the ports. But that's another story.
I'll be taking the amp to a friend's Thursday for a rehearsal, although a quiet one. But it will be interesting to try it in a different environment.
Don't judge me! 

