my deck (pioneer 6500) has two settings for my subs... normal and reverse... whats the difference?

my guess is that it switches the polarity on the speakers making them go backwards...kind of odd seeing that option but if you wire it backwards that would be an easy way to fix it.

does it hurt them at all if they are firing backwards?

i have the same deck, and for the life of me i cannot figure that out as welll, it might have somethin to do w/ switching the stereo chan. meaning if you accidentally hooked up the right rca to the left spot and then forgot when you got to the back.. idk..

What he said, changes the phase of the subs. You should notice a difference in sound when if you use it (wont sound as good unless your wiring is backwards.)

It is for switching the polarity of the subs. IN some cases that can make it sound better if certain freaquencies are arriving at your ear out of phase with the rest of the setup.