Just installed a cx501; interesting interface, it has a large spin wheel that clicks (meant to mimic an ipod). So far the sound is decent; I bought it for Iphone 4s integration. It works fine for MP3s on the iphone but doesn't like Spotify at all, at least through USB. Works OK on bluetooth, but it won't display the song title.
I picked it up for 185 on Amazon, not a bad price for a double-din unit.