heres what i would do.
get some dry marco rock and scape your 125g in your new house. when you do a water change, use your waterchange water and put it in your 125g. then fill up the rest of it with salt mix and ro/di water. take some pieces of live rock out of your 55g and put it in the 125g. use new dry sand, not live sand. your established live rock will side your dry rock and dry sand. let it cycle itself, add a shrimp to help it start ammonia. once its cycled, transfer everything else over. stirring up established sand will release pollutants into your water and can cause a crash.