I think you're on the right track though - Swap out stuff and see where the problem is by a process of elimination. Be sure to check out your connections, although I know I didn't need to tell you that. Pay particular attention to the tightness of the spade lug fit. I like them to be snug, and if not, I'll gently compress them with needle-nose pliars. Be careful to brace the connection on the speaker as you're installing or removing spade lugs though - the fiberboard that the lugs are attached to isn't very strong and you can easily break it if you push hard enough. And I doubt Eminence would warranty broken fiberboard caused by pressing the connectors too hard.

My experience with Eminence is that they have exceptional quality control. I've never had to send back a single speaker due to acoustic problems. But if you find that one of your components is the problem, we'll sure be happy to warranty it for you. There's a first time for everything.