I'm looking at replacing the factory radio with a head unit that is satellite radio ready.

First, could someone confirm for me that the factory radio in the 2005 Limited Coupe is NOT satellite ready?

Second, I went on Crutchfield.com and narrowed (from the 100+) it said would fit my Crossfire to 11 choices. I then did the side by side compare. One of the only differences among them seems to be the preamp voltage (some are 2.0, some 2.2, some 2.5, and a few are 4.0). Someone told me that 4.0 is better but that it can overheat the car. Any truth to that concern? What voltage would you get if you were me? - there's not a huge price difference between them. How much does the voltage affect the sound quality?