I recently installed the Seidio Powered Swivel Mount. They are currently offering a bundle that includes a number of different mounting options. All I can say is WOW - very nice. Also relatively easy to move from car to car. I use my iPAQ for MP3, AudioBooks and GPS. With the built-in speaker/amp, I can clearly hear my GPS even with the radio on! I've very happy with this purchase. The web site is:
http://www.seidioonline.com
Good Luck.