Hey Brian,
I might have missed it in another thread but you didn't mention the size of your old tank and the new one here. Most off the good bacteria that will keep your new tank from going into a cycle is on the surface of your live rock and in your sandbed, not so much your water. Your old water is good for your livestock as it is used to its parameters already. If your new tank is bigger and you are having to add a lot more water, your new tank will likely cycle especially without your old live rock. Also, depending how much new water you are adding you might want to drip acclimate your coral to prevent shock. In any case I would keep some bacteria, clean saltwater, carbon, and maybe even something to fight ammonia and nitrate if you are adding your livestock to the new tank without giving it time to cycle. I would hate to see something spike in the middle of the night and you be without the tools to offset the problem. Good luck with the new build!
-Nick