I'd be a tad concerned if the cap looks dented, though I have no idea if this affects the sound. One wonders about the handling that got it in this shape.
Because speakers like this usually have no grille, it's easy to squeeze in the wrong place when taking them out of the box -- hence, a dented woofer cap.
I've heard about a trick of using a piece of tape to latch onto the cap and gently coax it back into position. Tweeter domes help with accurate dispersion, but I don't know if woofer caps do anything acoustic.