If you have a big amp with plenty of "good" power, not a crapy amp, but a quality one pointing them forward will get you more punch, but if you do not have enough power you will hear distortion really badly. If you have a lower quality amp then face them backwards and you will not hear the distortion, and the rumble will be louder, but the hit will be delayed because the sound ways have to reverb back into the car causing the delay.
So the moral of the story is, buy a good quality amp and put them in a fiberglass bowl in the back like I did.
