I own a 2011 Cannondale Jekyll 4 with a 3x9 sram drivetrain including an x9 rear derailleur and x7 shifters. I was going to upgrade to an XO type 2 rear derailleur because it has a clutch system, which would eliminate chainslap. However, I found an XX rear derailleur for cheaper. Assuming that I would have to convert to a 2x10 drivetrain (I'm pretty sure I would have to, but not positive, hence the thread asking for help), what is the bare minimum of drivetrain changes that I will need to make in order to have the XX rear derailleur working right and be able to add a chain tensioner (also assuming that this eliminates chainslap; correct me if I'm wrong) further down the road when I have enough money.
By the way, the specs of my bike can be found here: http://mountain-bikes.findthebest.com/l/275/2011-Cannondale-Jekyll-4
Thanks