On the Q9's 6.1 is as high as you can go. There is no more official support in terms of new software updates. I would encourage going from 6.0 to 6.1 there are many improvements including battery life, performance enhancements and new features. Check out
this article for more.
WM 6.5 only comes on new devices such as the HTC Ozone/Snap, Samsung Jack, and some others. Very few devices received updates from 6.1 to 6.5