The MEX-BT5700U is designed to occupy one DIN—a standard unit of measurement for car stereos, about two inches tall by seven inches wide. The vast majority of cars on the road have either a one-DIN or a two-DIN opening in the dash for the audio system. My car, a 2004 Kia Sedona minivan, has a two-DIN spot, so the custom-stereo installer used a spacer pocket to fill and cover the extra space. The unit Sony supplied for this review fit well, with installation taking about an hour.

A CD-R/RW-compatible CD player rests behind the head unit’s faceplate, which can be removed for security (a hard carrying case is included). The system’s AM/FM radio tuner provides 18 FM and 12 AM presets, accessible via face-mounted controls or the included wireless remote. —a digital, terrestrial radio format with clearer sound that lets you “tag” songs for later purchase using an iPod—is a $150 option. You can also hook up a satellite-radio tuner using a separate $100 Sony UniLink-bus adapter.

A front-facing USB slot on the head unit lets you connect just about any USB-compatible MP3 player, including—via a USB dock-connector cable—any iPhone, iPod nano, iPod classic, or iPod touch for both playback and charging. Setting the source input to USB lets the head unit read the connected device’s contents and display them on the head unit’s screen. (If you’re using an or a very old iPod, you’re not totally out of luck, however—there’s also a 3.5mm auxiliary-input jack you can use to input audio from any device with a headphone jack.)

One minor complaint here is that this USB port is in plain sight. This means that when your iPod is connected, there’s a big cable dangling out of the dashboard. Compare this to the Pioneer unit I have installed in my other car, which has a USB port on the back: I’ve snaked the dock-connector cable from the back of the Pioneer unit into the dashboard glove compartment, making the wiring unobtrusive and keeping my iPod hidden from potential thieves when I park.

You navigate your iPod’s music content using either the controls on the head unit or an included wireless remote control. I have a 160GB iPod classic that hosts over 12,000 songs at last check, so navigating using the head unit was clumsy at best. You can use a “Jump” feature to automatically skip forward a specific number of songs on a playlist, but this doesn’t make the navigation of large lists any easier. This unit needs some sort of fast scrolling feature, similar to the way that the iPod will let you scan alphabetically through artist and album lists when you spin the Click Wheel rapidly.