I just put a 700 unit in my 2008 Cobalt. It cost me about $150 in installation materials. I installed the unit myself along with subs and HD radio box (bad implementation, but that is another thread). I just about nixed the project as there is no reason for someone to have to buy a $120 box to connect a radio to their car. I would recommend in your situation (to keep it cheap and less intrusive to the car's wiring) is to just route the audio to the input on the stock radio and use a speaker to line level adapter to add the subwoofers from the rear speakers. Most amps have them built in an
