If you're looking for a head unit with usb or SD card, Blaupunkt makes a few. I've got a melbourne with the SD card in it, and I think the St Louis(?) has the SB port in it. You can probably get one on ebay for a decent price. Mine was +/-$100 to the door. If you need instructions on how to install it, there's a thread for that. Most of what it entails is cutting one wire to unlock it from the telephone setting, the rest is fairly simple and you can do it in minutes.

Yes, there is an amp in the car. It is located in the passenger side floor board behind where you would normally put your feet.