I am working on upgrading my audio system. I have replaced the front dash speakers (Dealer item only) and both door speakers (Alpine). With the dash speakers now working... the driver's side audio is distorted. I am thinking the output of the head unit is screwed. They call it a double din unit.

First Question, what's the deal with the DVD's in the head unit?
Second, Does anyone have Nav in theirs? (seems a great upgrade and has the space to build it in)
Third, Double din vs Smaller unit and storage underneath
Last. could my problems be the amp under the driver's seat? and should that work with the head unit with out alot of fuss.?