But, just because you have the CAT button on the radio doesn't mean it has XM. I have that radio, which means the radio itself is capable of playing XM, but I do not have the receiver. It's located in the rear quarter panel between the body and the interior trim.

 

Still researching this. Which models will play mp3 discs? I'd rather just have a stock radio so I don't have to mess with all the adapters. I'm going to go ahead and upgrade the door speakers. Will there be any difference sound wise between the different stock head units or is it just bells and whistles (XM, 6 disc, etc.)

I'm not wanting a lot of base (I'm old), but I wonder if a small Kicker tube in the back would add anything? It looks like they have a cheap adapter to hook it in easily to a stock system. Any experiences?

 

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But is that one the only mp3 version? I didn't know if the 6 disc head would, or if you had to have the 6 disc changer with that one.
I guess if all put out the same power and there's no sound quality difference, I'll skip the mp3 and focus on speakers.