Assuming you have the auto dimming....on the 2011...what would it cost to add the backup
You can use this for steering wheel controls Amazon.com: Metra Axxess ASWC Universal Steering Wheel Control Interface (Black): Automotive
And I would suggest doing so.. Not too complicated to install when taking out stock deck. And if you accept you are replacing the stock deck honestly job gets alot easier in some ways.. I personally go after a cheap 4/5 channel amp like MB Quart or Cadance WoofersEtc.com - F100-5 - Cadence 5-Channel 1800 Watt High Power Amplifier
or WoofersEtc.com - ZRS-C8 - Cadence 2000W 5-Channel ZRS Type C Series High Powered Car Amplifier
or MB Quart ONX4.125 - 1000W RMS ONYX 4-Channel Car Amplifier/Amp
then run whatever speakers you want and whatever sub you want. Just remove what currently in the car. Then looking at one AMP kit and one AMP install.. Running RCAs back to AMP and then speaker wire to all the speakers.. Work yes.. Hard no.. Trying to mod the stock unit is a pain and wont sound as good.. then down the road if you want to install a processor in the mix you are processor ready.
2011 GT Coupe Premium | MT6 | 3.73's | Security Pkg | BREMBO | Comfort
Installed JLT oil catch can, Tint, Beltronics RX45/shifters