if possible I would try to avoid putting th amp under the seat because it will be difficult to filter out the heat. Your best bet is to buy a small sealed box and you want to put it right up against your back seats with the sub facing the toward the rear" facing you when you open the trunk". If you get a sealed box and say you go with a 10 in. sub the box will be a minimal size and you can put it against the back seats on either side of the trunk. As far as the amp goes their are so many things you could do. But all would require custom work. You could have it mounted on the side of your trunk standing up. this isn't too difficult and it would be out of the way.
