Technically the speakers in the back are subwoofer type if you have the upgraded system. You could possibly add a different type to the wiring and add extra amp for it.
On the Sedan, yes, it has 6x9 "subs", whereas the Hatch has a tiny little "sub" that has a large enclosure under the load floor.
The sedan's setup is the same as the Pioneer system in the 1st gens, and the common upgrade if you did not want to go with larger subs and a box was to replace those 6x9s with Tang Band 6x9 subs, and amping those.