Personally I would move everything at once. Since your live rock is cured and will only be out of the water long enough to move it, there should be no cycle. The water is not what keeps your tank stable. It is the rock and the sand if it is live. If you are using new clean sand it will not cause a cycle either. If you plan on using old sand that is a different story. Just think of it as a tank move but into a new box. I would just make sure that the new water you are using has been mixed for a couple days and the parameters of PH, temp, CA, and KH are as close to the old water as possible.