I just did it last week, My main concern was to keep the OnStar and Steering Controls.We installed a Pioneer double Din on my 2005 Cadillac STS. http://www.pioneerelectronics.com/PUSA/Car/DVD-Receivers/AVH-X8500BHSwith the help of the PACS installation kits, http://www.metraonline.com/part/GMOS-13, I was able to preserved my steering and OnStar controls, by the way I gain Bluetooth from Iphone 5, Pandora, HD Radio, SD card, DVD and USB, and apps like Waze Navigation and Opera internet Browsing just to name a few.We used an Escalade Dash Kit and it looks like the factory dash.We Left the center channel to the old Bose amp for OnStar use, but replace all the speakers, fronts are http://www.pioneerelectronics.com/PUSA/Car/Speakers/D-Series/TS-D1720Crears are http://www.pioneerelectronics.com/PUSA/Car/Speakers/D-Series/TS-D1602RSub is a Bazooka Double amp 8" Sub Tube to replace factory sub that fix perfectly in the trunk.http://bazooka.com/products/mobile/Amplified-Bass-Tubes-Subwoofers-C6/BT-Series-S68/BTA8250D-DE---BT-8--250-watt-Double-Ended-Class-D-Amplified-Tube-P41I also installed all LED's HID's, Turn Signals, Daylight Driving Lights, Fogs, License Plate, Reverse and Interior Dome's and still do the Dimming, It Looks great. http://www.carid.com/led-lights.htmlWe Installed an STS-V Classic Mesh Grille from EG Classics. http://www.egclassic.com/inventory/item.php?itemid=88also addedd 2, 7" Monitors HeadRest with Infrared Wireless Headphones. http://www.audiovoxproducts.com/headrests/universal/?sku=AVXMTGHR1MThe installation was done by JR Electronics in Miami, Florida Tel: 305-226-1660. http://jr-electronics.com/PIONEER.html talk to Patrick... 2005 Cadillac STS factory Radio Removal while keeping Controls Done!!!