One thing for sure, you will need to upgrade your front tweeters too. Higher frequencies need to be around at ear level. This is the first time in my 20 years a menufacturer suggests you to kill the tweeted in favour of a tweeter in the foot area.
Kick panel speaker arrays work better for stereo image as the mids and highs come from the same plane. However, kick panel speaker mounting requires aiming both mids and highs at a certain angle to raise the image to ear level. Mounting co-axials into the foot well off axis is not a recommended method of achieving proper staging.