the two mote common things I do in that situation is just remove them for installing a real sub, the extra height can help a little to be able to push some boxes further back in the trunk under the rear shelf.
or replacing them with full range speakers, disconnecting the rear door speakers, and rewiring it so that the new speakers are now the rear speakers, the lower rear door is such a terrible location because of how low they are, all sound coming from them just gets so muffled. however without a real sub, this causes you to lose so much of the deeper bass that the factory subs produce.