When I put in my subs, I tried with the subs facing the cabin up against the back seat, then I flipped the box 180 degrees and had the subs firing towards the taillights and it sounded 10 times better. My experience is that with a sealed enclosure (what I have), you don't want the subs firing close to any panel of the car. It does something the the sound waves which affect how loud it sounds. If you have it as far away as possible from any panel or wall, it will sound that much louder and that much better. Should you decide to have your subs firing into the cabin, I can't imagine that damaging you amp in any way, you should be just fine.