The rear speakers are a ***** to get out of a 97 Civic coupe. Pull the back seats, pull the rear seat side trim, then pull the rear deck, and THEN you can remove them. Crap, I need to hurry up and get them out of there before it starts to get hot down here.
The loudness is determined by wavelengths - you want the peak of the wavelength to be at your head for a certain frequency. The lower the note, the longer the wavelength. So the sound needs to travel longer to get a more pronounced lower bass.
That means, move it to the far back, facing the front, or face it against the rear, so it bounces off the back of the trunk and goes forward.
Seats down allows the sound to pass easier, so yes, it will tend to help.