Sorry a I'm a bit late but...
I had a Hitec HS-645 in my CRT.5 and found it a bit slow.
I've put a HS-7940TH in my new build and love the speed but I wonder about the quality. See this youtube vid of the brand new servo for the audio of the crunchy gears...
http://www.youtube.com/watch?v=KEkhzjwSnXw
Next time I might try a Futaba BLS-451???