The title for the fastest SUV (just over 200 mph) goes to the Barabus V12 GLK. The bi-turbo V12 and all the goodies to keep it on the road and stop within the same zip code come with a starting price of over $570,000. But think of the bragging rights.
This rig has tremendous braking power. Watch this video on brake service to be sure that your vehicle is up to the task.