i wanna face my sub towards the cabin of my car in the trunk but my amp is screwed to the backside of the rear seats. This means that the sub will be about an inch away from the amp and blasting music at it constantly. will this damage the amp in any way? Will it sound better if the sub faces teh cabin?

 

No it sounds better if you face the subs away from cabin. Your trunk acts as an enclosure itself.

 

I've heard different opinions from everyone, for my car (civic) I pointed the subs toward the cabin, upward, and to the rear, and facing the rear was the best.

but honestly, you should experiment with each setting.
I remember hearing that having the sub face the rear and have the box only a foot or two away from the rear of the car is the best option. but I haven't tried that

 

That does tend to work very well, but makes the trunk lid rattle like hell cause the sub(s) are so close to it.

What also sounds pretty good, is face the subs tward the front of the car, but push the box to the rear of the car... tward the rear bumper. You get a lot less rattling outside (especially if you dont have any damping) and the sound is still powerfull. If you put them close to the rear seat, facing forward, you tend to hear a lot of "barking" from the subs because their air space is kind of constrained.

 

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.

 

facing the cabin whichever way is something YOU will have to do yourself. facing towards the front, back, sides, all that stuff will depend on your car and ears.

and putting the sub that close to the amp, you want to make sure that the amp wont slide into the amp, or the woofer getting damaged in any way.

 

will aiming the subs up or down (roof of the trunk, floor of the trunk) make a big difference? just wondering

 

yes, it can make a huge difference, and not neccessarily a good one either. It's all about experimenting with it, see what sounds best to you and leave it like that.