Another Aftermarket radio ????

[Orazids]

So Im sure it has been answered but just wanting a def. answer for what Im doing. I am goinh to replace my stock cd player not the monsoon system with an alpine headunit.With that there will be my Sirius radio and Ipod chord. I will also put an amp and sub in later.

I want to keep all the chimes and onstar capabilities.

I looked and I think I amd going to go the Soundgate digistar route. Will this plug straight up to my alpine or will I need another harness or one specifically for the Alpine??
Do I need to get an adapter for the AM/FM antenna also??
Will the factory XM antenna work for the sirius??