I am preparing to purchase a 2011 Trek Madone 5.2. I like the look of the Dura-Ace 7900 crank better than the Ultegra 6700 crank that it comes with and am considering upgrading just the crank. I've installed square taper and external bottom brackets but am unfamiliar with BB90. In the pictures on the trek website BB90 looks somewhat like the BB30 press-fit system. To do the upgrade, would I need to purchase a special Dura-Ace BB90 crank and some kind of BB adapter hardware (if they make this ... it's not on the Shimano website)? Or could I just purchase a standard Dura-Ace 7900 crank? Is there some kind of press-fit with Trek's BB90 or would it be a pretty simple installation? Thanks.