Here's a link to Motor Trend's X6 test drive (originally posted by LeMans, as usual):

http://www.motortrend.com/features/a..._preview_drive

and here's the interesting bit:

The cargo room behind the rear seats is equally impressive given the roofline. The deep trunk looks as though it could swallow several large suitcases, and there's under-floor storage similar to the X5's.