You have to unlock your phone if you want to run 6.5 at this point. The only way you wouldn't is if sprint/htc decide to provide an official upgrade at some point in the future. Just download this
ftp://ppcgeeks.com/Diamond/Users/Tob...20Unlocker.rar, run it, to unlock, then you'll be able to run any of the custom roms. Most of the custom roms come with the rom update utility which is almost just like the HTC provided roms. Just run custom_ruu.exe and you're good to go.