Hey,
So I got my car back with the new tweeter location (yes I didn't do it myself, yes I hate 'allowing' others to touch my car, but I was out of the country at the time and it had to be done by someone other than me).
So the sound is much better. I highly reccomend the knee height mounting position. Yes you need to cut the door, but it is worth it. The shape of the door adds a neat 'stereo' imaging factor that 'hides' the location of the tweeter. Some find this horrible, others like it. I like it since it adds a more ambuient feel to the system. Now when I crank it up, the sound is just clean and clear, with no high or low bias. (The tweets are tilted up slightly, not aiming at my knees. Sort of at a place in front of the center rear view mirror.)
Seth