My long frustration with the lack of an Aux input on the stock Infinity radio/CD unit finally ended today, when I replaced it with a new Kenwood KDC-X599 which I purchased from Crutchfield.

My experience with Crutchfield was excellent. Although I was leaning toward buying a German brand, I decided to ask for their advice. My advisor recommended the Kenwood KDC-X599, which was not on my radar. He clearly knew way more than me, because after I compared the Kenwood to other units, I realized that his recommendation was spot on. Plus Crutchfield provided this collection of freebies: installation instructions, MB extraction tools for the Infinity, connection harness, antenna adaptor for the new unit, and 3 day shipping. Good deal. I’m a happy customer and can highly recommend Crutchfield.

The KDC-X599 supports Bluetooth, which was a bonus as it was not a must have for me, so I got to mount the mic and run its cable. I mounted the mic at the top of the A-pillar trim following the guidance in

Kennwood D562BT Replace Oem Infinity w-o Nav Easy Install

The biggest challenge is snaking the mic cable through the dash. Rather than using a coat hanger or electrical fish table I used a 36” cable tie. A cable tie is less likely to do harm.

Useful pieces of information for others doing a swap:

• Removal of the trim on the A-pillar is as described in the aforementioned thread. See pages Interior 23-161 to 23-163 in the 2004 Service Manual.
• The Kenwood has front, rear, and subwoofer outputs, but the connection harness only has front and rear plugs. I initially connected the front and rear plugs, but noticed that the speakers behind the seats were not live. (Those must be the subwoofers mentioned in the Crossfire manual.) So I moved the rear plugs to the subwoofer output. Works fine, but there may be a pair of speakers somewhere not being driven. (Does anyone know for sure?)
• The stock Infinity system has a power amp, so you need to connect the power control wire on the connection harness to the new unit’s harness.