Okay so I know that's not a technical term

I'm looking to replace the factory radio (with the same model) because the front outputs are having issues with an occasional distortion. I thought at first it was the speakers but some times you can power the radio off and it goes away so something is wrong with either the internal amp or the logic board itself. Is there anything I need to be aware of before picking up another radio? I have the Pioneer system with OnStar and I'm concerned about making sure I get the right model. I saw a few on eBay (assuming I would need to contact the dealer for codes) that were XM ready with MP3 but they mentioned nothing about being the premium system.

This is going in a 2006 LT.

Any help would be appreciated! Thanks!

Kelly