What do I need to do on an HTC One X ???

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http://androidforums.com – Hi Everyone, I hope all is well with you guys/gals! I'm a new-be so please excuse my ignorance. I want to buy an HTC One X that is already unlocked (I'll be going to Europe & staying awhile). I then want to root it. I found an already unlocked phone from a major retailer & want to have it activated through AT&T. But then I looked on Amazon & found what they called the International Version but they said it runs slower than the US version)? Which one should I get? Does the US one work in Europe? Now as far as 'rooting' when I went to a rooting site it said the rooting didn't wor (General)