I don't know if I have a picture of them, but for years I ran a pair of off-the-shelf Pioneers that were intended to be rear shelf mounted. They were 3 speakers in a long rectangular housing, somewhat wedge-shaped from front to back. The woofer was probably 5". Anyway, they fit perfectly in the space between the seat bottom and the side panel. Facing straight up, the sound filled the fishbowl -- they were awesome when loud but you kind of lost the subtleties at moderate volume. They really needed front speakers. With a pair of 4" replacing the oval dash speaker, and a pair in the kick panels, you'd really have something.
