SurrealSymbiont

Alright. So I'm going to post a bunch of pictures of what I've got as well, but here is a rundown. (Disclaimer: I don't know anything about car audio, so please ELI5. I'm a computer guy, not a car one. I'm also going to bombard you with a WoT so you can get the best idea of what I am dealing with.)

I just picked up a car, a 2001 Audi A4 B5 model. Love the car. When I got it I saw that it had what I assumed to be part of an aftermarket sound system in the back. I learned it was an amplifier. Kicker 700.5. Guy I know said it's a good part. Problem is, while the sound plays in the car, it sounds like some of the speakers are either blown, or going to soon. Also, there was no woofer or anything. That guy I know said it looked as though the system was put in professionally, as the cords seem to be rigged under the carpet somewhere that is inaccessible. The amp has power. There is also (I assume this is not stock, ha) a switch just to the left of the stickshift which, when turned on, allows for aux in, as long as the radio is dialed to FM something or other.

Last night I replaced the speaker in the driver door and it is working. Long story short, I cannot get the woofer to work. I am not even sure what any of the particular inputs do on the amp, and I don't even know if the amp is doing anything except shining pretty red lights.

Edit: Oh yeah. Even with that new speaker in: It feels like the volume **** is not turning up all the way. If I crank it it will turn up and I'll just get a very brief instant where it sounds louder, then backs down. What gives?

I also intend on taking out that radio (header? Deck?) and putting in an aftermarket one with Bluetooth. (3.5mm jacks going out on my cell phone; I get tired of that...)

Edit: something I forgot to note and post a picture of. I will if it is relevant. As you open the trunk, directly on the left, there is a CD loader.

surrealsymbiont's uploaded images - Imgur