I'd recommend staying wirless. Since you say you're in the car for this, get a BT speaker if your car doesn't have it built in and use that instead of a headset. First, you'll get longer use times between charges on most of them, you can get units that are not battery powered, instead they plug into the 12V outlet permanently. Second, all, or at least most, of the battery powered ones will work when plugged into power as well. Third, since they're designed for in-car use the good ones will have better optimized noise reduction than a headset.
And fourth, the headset jack on the Droid X sucks. I've tried three mid-to-high-end headsets on my X, an in-store demo X and a friend's and they all sound like crap. The same three headsets sounded fine in my unlamented Blackberry, my iPod Classic, iPod Touch, and a VZW employee's Thunderbolt.