There are a lot of ways to mount and power a radar detector. The lower center of the windshield is a good place if the unit will be powered by the electric lighter.
Putting the detector up near the rear view mirror is good if the power cable can be hidden around the frame of the windshield. In order to connect Escort into the car's electrical system, we needed the Direct Wire "Smart Cord" ($30) kit.
We kept the other SmartCord for when we need to use the detector in another car. We also ordered another windshield ($4) mounting kit for the same reason.
To power the detector, we needed to run the power cord from the top of the windshield down around the left side of the driver to the panel in the photo above. In the Boxster, there is an extra power plug on the driver side console. The green wire with the black strip goes hot when the car starts. This is the one we tapped (red wire from the SmartCord) to power the detector. We grounded the black wire of the SmartCord to a metal piece on the console.
The remote of the SmartCord fits nicely between the space under the radio and the storage compartments. Its location also made it much easier to use and see... especially nice since the detector is now located higher on the windshield.