Here is the main issue now....I have until 7/24 to return my iPhone 4. How hard will it be to actually get a Droid X. on 7/15? My understanding is that some people who ordered their htc Incredible's are still waiting.
According to the CSR from Verizon I talked to this morning, they beefed up production on the X's to prevent the issues they had with the Incredibles... She said mine should arrive by the 16th.... (Take this with a grain of salt, as we are all aware of the reliability of CSR's, but this lady was super SUPER awesome, so I trust her ;-) )
As far as the car audio discussion goes, I would highly recommend using bluetooth audio or at least AUX versus USB. The only advantage to USB is that it charges your phone. There are several reasons I prefer bluetooth vs. AUX, for starters, there are no wires, and with my current setup I can control my phone from my stereo... play and pause, skip tracks, place/answer phone calls. Both Bluetooth and AUX will allow anything that would come out of your phones speaker to be passed through to your car stereo... be it music, streaming music, navigation instructions, even the audio from voice calls if you so desire. With bluetooth (if you're receiver supports the AVRCP bluetooth profile) you can get playback controls (play pause fwd back) on your headunit, and potentially on your steering wheel.
You basically have two options for bluetooth, for a purely wireless setup you could buy a bluetooth headunit, which aren't cheap, I went with the Sony MEX-BT5700, and I absolutely love it, I think I paid like 200 or 250
You're other bluetooth option is a product like the Kensington LiquidAUX Bluetooth car kit. These things used to be like 25 bucks, but it looks like they are running around 75 now.... The Blackberry Remote Stereo Gateway should also work, and those run about 50 bucks. You can look for other products that fit your specific needs, just make sure they are at least A2DP capable for minimum functionality.