its just ground noise / engine whine. get a ground loop isolator it will help alot. the $15.00 ones from radioshack work decent for our aux inputs.

 

both oem navi and rockford fosgate system are pretty awful imo. The nav screen is crusty looking and makes stuff hard to read in sunlight. As for the rockford fosgate, the sound is not clear at all and its just loud without any clarity. You can invest your money in something more usable.

 

Some people seem to have bad luck with the OEM. Mine is great though and people comment that music sounds better in my car. The nav is very usable also.

I'm not sure why some people seem to think it's so bad or what they are trying to listen to that sounds so crappy. Satellite radio sounds pretty good and CDs / ripped music sounds great. No problems with the Aux input from ipods either (2008 MR). I imagine the ipod dock for the 2010 just makes it better.