Best Interface Kit for 2009 G6 without Center Volume Knob.

First of all, I have Googled 'til I'm blue in the face. (iDataLink, Metra, PAC)

I had a Pioneer AVH-P4900DVD with the Metra DIC Kit, Pioneer XM adaptor, and the PAC SW1 kit. The head Unit screen went bad.

So I am going to the Pioneer AVH-4200NEX Unit. I want to maintain the factory DIC, SWC, OnStar, XM, and amplifier in the car.
What kit do I need to get ?

Thanks in Advance for your help...