Also, if you're interested, I'm running the following system in one of my older cars -



It's the Sony MEX-BT5000. I actually picked this up off eBay for ~$400 back nearly 2 years ago. Should be hell of a lot cheaper now. It doesn't do USB, however if you're anything like me, since I work with cellphones all day, I tend to keep all my music on my phone. This headunit will let you stream music over bluetooth from your cellphone to your headunit, while also giving you the call functionality from there too.