I want to install rear speakers in my 99 legacy brighton wagon. There are mounts for rear speakers in the rear doors. I'm wondering if any of the pre-existing wires that I see in the door are speaker wires?

Look for a taped up connector. If you can find one, that is probably for the speakers. If you don't find a connector, the speaker wires are probably not there.

my general rule of thumb is this: if it was offered as an option when the car was new, then the wiring is probably there.

 

i haven't proven this wrong yet, but i've only owned 6 subarus and didn't add anything to 4 of them, so i could be wrong.