I personaly love 3 way systems. In most of the cars I have listened to or worked on the best were 3 way systems up front or waveguides.
Anyway, find an installer who can do some fiberglass and put some speakers in your kick panel (by your feet). If done by good installer you can get a really good sound stage.
Something like this would be great. Sadly doesn't look like they make a model for our car. With that said there are plenty of shops/people that could make you a set.
Nissan Maxima Component Speaker Kick Panel [QL-K8002B] - $189.95 : Q-Logic Direct, Car Audio Speaker and Subwoofer Enclosures
Whatever you do. As bigaudio already said, do not use the rear locations.