In the kick panels would be the only suitable location that I can think of.
DBZ, if you are going to put something in your dash like that, a simple dome tweeter would be a better option. Below is what the dispersion of the drivers would look like. As you can see, the output of the driver on the right would be difficult to hear.
[img]http://www.fototime.com/{14647B05-579F-44CF-9F6B-C4A165D2C80E}/picture.BMP[/img]
Maybe Luke can post a drawing of his focus to clear things up a bit.
