Media :: Playing Music Through Sony Car Stereo

So, this is a specific and detailed question, so I'll try and briefly give context:

I currently have the prior generation of this stereo in my car (don't know my exact model number, but it's basically the same as this deck: Sony stereo.

I connect my iPhone 3G through the usb port and it charges my phone while allowing me to access my library and scroll through artists, playlists, etc through the deck.

I am curious if the Droid Incredible can also do this.

I went into the Verizon store today to try and see if it can work and we had some issues. My deck can access the phone's contents if, when connecting via USB, I have the phone behave as mass storage (the rep was doing it, but said when you connect the phone you have the option to treat the connection as mass storage). So, I could flip through what seemed to be directory folders through the stereo, but I believe I could only access the phone's internal memory. I haven't had an android phone, but I assume mp3's are stored on the microSD. Am I correct in this?

So, is there any way to make the SD accessible through the car stereo so I can play my mp3s while charging my phone through the USB? This is actually a fairly big deal to me as I am in my car a lot and using the phone in this way with my stereo keeps me from having to have 3 different chargers (1 for home, 1 for messenger bag, 1 for car). But, if there's a way to do it, I can get away from the iPhone, and more importantly, ATT.

I know I have the aux input, but I'm only concerned with the USB for its charging properties.