Radio Shack Ground loop Isolator FOR THE WIN! It works perfectly and removes about 99% of the noise with no appreciable loss in sound quality....Although I did have to buy a stupid $6 Phono to 1/8" adapter like I suspected. Total came out to $24 after tax, bringing my grand total to $370! :O
I could have waited and bought one off of ebay for about $12, but I still would have had to buy the adapter, meaning I only would have saved about $6 bucks.
All in all, a good day in the build. I passed the in-car charging and audio test. Thanks for the tip on the isolator Scrambles!