shortening the photoperiod is the simplest way and will work fine.
If you are going from bulbs that are 1/3 of the par of the 10k's that you are changing to, which is quite possible if you are going to 10k xm's for instance......i would just cut it in half, then add a 1/2 hour every few days until you are where you want to be.
That should be plenty gentle of a transition
I just recently did a similar change on one of my tanks. All of my stonies were fine with it.......i did end up having to move some zoas down as they simply werent ever going to tolerate the new light as high in the tank as they were