Check out the link below for some details on BMW's upgrade announcement for the X6. Would hope a similar offering for the X5 would be in the works. +40hp/+37tq sounds like a minor tweaking given the potential of the 8TT, but its a start. I'm sure a more aggressive tune from Dinan or others would add 50-75hp or more and plenty of torque.
The conventional wisdom for the 6TT engine is that it is underrated at 300hp, so the actual gain may be slightly less than +84hp for Dinan tune. Still a nice step up in performance. I have not seen any specs on a prospective tune from Dinan, though apparently there is an X6 out there that Dinan did some development work on. A web search can take you to a couple of related discussions.
BMW Performance releases accessory line for 2011 X6 — Autoblog