How about properly deadening and sealing your door before you run and buy more drivers? You can have the best equipment and have it sound like garbage if you dont install it properly. Treat the doors and see where your current midbass stand. If they still arent what your after upgrade to a single better driver or to a larger driver.
Also as your setup currently sits you should be crossing mids at or above 80Hz. Subs anything under 80Hz.