You can flash straigh to CM9 as long as you follow the instruction set my CM9 rom, which will be somthing like, save rom to root of your sd card, boot into CWM, then do a full wipe, cache wipe, then flash the rom, also remember to install Gapps. You may also want to backup the rom you are using now, just to be on the dafe side, but problems dont happen that ofen, as long as people carry out the correct procdure.