I'm using the OEM CD NAV unit with a Nulaxy Bluetooth FM Transmitter (available from Amazon for $14.99) that plugs into cig lighter. Plays all my itunes through bluetooth through an unused FM band. I also have the ability for handsfree phone through bluetooth.

I find the OEM sound system really very good. The quality of my iTunes music is excellent. I've played CDs through my unit and again, exceptional sound quality.

I was also going to replace my unit so I could have bluetooth and iTunes capability, but after I installed the Nulaxy Transmitter, there is no need to replace the OEM Radio/CD player.

Here's link to Amazon: