Stick with an iPod for playing music in your vehicle. Smartphones, as good as they are, simply don't amplify your music enough to sound decent through components (even with a decent music player like PowerAmp). With an iPod, you can buy a head unit that is iPod ready, meaning there is a proprietary hook up and not connection via auxiliary cable. There is no proprietary hook ups for any smartphone. The advantage of this iPod ready connection is that there is better "lossless" sound coming through your speakers. Generally speaking, compressed audio such as mp3 is already a lossy format, so you should seek to minimize that loss by sticking with an iPod. The sound is noticeably better.