DanTheMan
Been here awhile...
I do find that the frequency response of the center channel (it's the elongated speaker on the dash) is not as good as the door speakers. The highs are missing. Before I call that a fault, it might be by design in that typically as we listen to 5.1, the sound designers try to expand the 'spacial' nature of the sound and thus reasonably little goes to the center speaker.
The center channel, by design, would be of limited range/frequency response. It's purpose is to 'fill in the blank spot' in the audio field, but not overtake the placement (and audio that proceeds from) the mid-highs and tweeters placed elsewhere in the car. Ideally, you don't want to 'hear' the center channel (meaning you wouldn't want it to be the primary source of your audio feed), but if its not playing, you would 'miss' the audio in the sound field.
Another comment made above suggested that the center channel in a movie theater was for the dialogue, and that typically is correct. However, the logic system used in movie production (audio following action) is entirely different from audio recorded in the format suitable for our new chariots.
Dan :>)