I see what you are saying, but the headrest dealing with the mid range would give me fairly clear audio at high speeds (motorway for example). Car noise is always going to effect the quality of what I hear.
Nothing I will do will detract from the above. However, with only low range going down by my feet, the tweets being on the door card and mid range behind my scalp. The 'feel' of the bass will be felt and the clarity should over power that of wind noise at speed due to the distance between my noggin and high/mid range speakers.
I really need to get the door cards off to see just what is possible in terms of size. I'm happy with my tweets and the headrest speakers are fine.
At the moment, all 3 speaker channels are sharing low, mid and high. Thus sound clarity being heavily unbalanced and distorted. Which I am hoping the amp will resolve.
Bikes sold, time for Mazda fun!