My suggestion is to put some good speakers in and get an aftermarket HU possibly a DVD/Nav unit. Im running kappas in my doors and i absolutely love them. Best speakers ive ever had and ive had a ton of speakers including reference. I have a Alpine HU and im running the stock subwoofer. Its plenty loud and the stock sub is impressive when paired with an aftermarket HU. It would be a ton cheaper then what you were thinking of doing. See if you can get a used AVIC D3 on ebay or something they come with bluetooth, ipod integration, and nav.