I just installed a Pioneer DEH-P6800MP. It's nice. Does MP3/WMA/AAC, has decent stand-alone power, very sensitive SuperTuner III, full sub controls, iPod controls, and a front input jack.
The input jack is odd-sized though, it's 2.5mm versus the 3.5mm mini-jack on mp3 players. Got an adapter from Radio Shack. Also the jack is located so the faceplate has to be lowered to use.
The BIG multi-function knob/joystick took some getting used to and the adjustment menus are pretty extensive/complex. Also, no color adjust on the display, need to like bright blue.