Since my specific car came with the OEM Harman/Kardon system with MKIV Navigation I had to purchase the Single Din radio bracket and trim that centers the aftermarket radio. I also purchased the sunglasses holder that will go on the bottom slot below the radio.

You can get the Bracket and Trim from EAS: http://www.europeanautosource.com/product_info.php?products_id=1226

OEM Part #: 65900410495

Here is what it looks like, pic courtesy of EAS:

To make my aftermarket Head Unit work I needed to purchase the 5M Fakra cable which extends the audio power, audio connections to the front.

I was able to purchase the cable directly through Jeff @ Dynavin Solutions! for $55. Later on this will allow me to run a dynavin unit if I wish.

You can get this cable here:

http://jandtdistributing.com/dynavinsolutions/products/aftermarket-accessories/fakra-cable-kit/