car audio subwoofer installation?

[chris]

i was looking at buying a used subwoofer and 180 watt amp kit for my car. the seller is providing the box that houses the speakers and the built in amp. i was wondering what besides the box i would need to complete the installation,

would i simply be able to reroute my existing speaker wires to the amp or will i need to be providing an extra power source for everything to work properly. my existing head unit is the factory model for a saturn sl1 with the frequency control sliders on the front setup to output only speaker cabling, not a patch cable or rca.
i appreciate any help but i have no idea what im doing so i really need things broken down right to basics. also any thoughts on cost would be awesome

 

[zimzam]

If you're hooking it up to a factory car stereo, you either need a line-out converter to step down the output of the deck to a low-level signal or an amplifier with speaker-level inputs. You will also need to run a fused power wire (8 gauge should be fine) from the battery to the amp. A Ground wire from the amp to bare metal that's connected to the chassis, and also a remote wire that's connected to a 12v power source that's has power when the ignition is on not off.