Sean
the tweeter on one of my M3's has the same indent in the same general area, as well a couple of scratches. I had my mom swap the speakers a few times and I could NOT pick the one with the scratched tweeter.
One thing I realized, though, is that the light reflexting of the titanium through that little space in the X might cause it to look like a dent. Change the lighting around and see if it still looks like a dent.
If there is a dent causing a sonic difference, Axiom will probably change it for you.
Good luck, and let us know what happens!
