The XXX 6.5 works great for both midbass and midrange duty. Depending on how well sealed and deadened your doors are, how much power you are going to run to them, your bottom end crossover frequency, and driver axis alignment... We could suggest something for your application.
Basic suggestion: drop the pair in the door making sure things are well sealed/dampened and rigid (no front/rear wave cancellation and so your doors dont rattle apart. Make sure you have a decent opening for the pair to play through (dont hide them behind a tiny factory grill that was meant for a 4"). High pass them in a sealed/IB arrangement at 60 Hz. You can play up to 5kHz off axis or 7 kHz on axis. Depending on what tweeter you use, you can move the mid low pass down to match for better integration to the tweeter.
Now if you have TONS of room, you can always run the pair in .75 cuft tuned to 45-50 Hz and have more midbass than you will know what to do with.