There are many CFW for Nokia X6 such as Symbian Anna 7.5,Nokia photon,Photon C6-05(It's good). I also have Nokia X6 and flashed it many times with CFW. It's Just not that risky if the steps are followed correctly..
By the way the tutorial link Google Translate
Hope this may help You But Original FW is better cuz it doesn't has any QT issues and other bugs But trying a CFW is gud