You can do it, snail on this site did it to his 96 coupe, which I have seen and driven. However what he did was relocate the A/C controls to the center console, and where the controls are on the 99 I think he made a fiberglass panel or something and stuck a couple of tweeters in there (not the best imaging obviously, but it fills the space). PM him for info, or I will direct him to this post.