Pioneer's AVIC-D1 (shown) is an off-shoot of the company's AVIC-N2 but designed for use in cars with a double-DIN sized chassis. These nav systems were a hit at CES because of their do-it-all capabilities, but they also come with a steep price. For $1,800 MSRP (screw the kids' braces), the AVIC-D1 offers DVD-based navigation displayed on a 6.5-inch motorized LCD that flips down to reveal two disc slots. While both the N2 and D1 allow you to play CDs while still utilizing the nav functions, only the D1 with its double disc slots allows both a NAV disc and music CD to be loaded at the same time. Nice touch. Both systems offer features like XM NavTraffic, which displays satellite-based traffic information that's taken into account when calculating routes, and rear-camera capability, but the former requires a $330 GEX-P10XMT XM NavTraffic Satellite Radio Tuner and an XM NavTraffic subscription, and the latter a $300 rear-view camera. One feature of the N2 and D1 that Pioneer doesn't even list on its website is the Vehicle Dynamics Monitor, which displays information like acceleration, lateral G-force and angular velocity in gauge-form on the LCD. That could turn a trip to the grocery into a GT4 License Test.