A couple n00b questions

[Big Papa]

im doing a build in my taurus soon. I'm having a hard time deciding wether to do 2 12's or a single 15 in the trunk. I've had a single mofo 15 off 1500 watts before and i loved it but i wannna switch it up. if i went for a single 15 again, it would be another mofo. if i went the route of 12s i'd get american bass tnt's.

my other question is which way should i point the box? either way i go its gonna be subs up. im just not sure whether to fire the port back or into the car.