upgrading 55g to 65g with sump

I feel I can give you pretty good advice because I recently upgraded from a 65g total water volume to my current 150g total water volume. I did it pretty successfully and only had a very small diatom cycle. I was able to transfer all of my reef and fish in one evening. What I think helped most was using all of the live rock that i had and using as much "live water" as possible from my old tank. During the transfer I put all of my LR in several tubs with a powerhead and heater and took it out of the water for as short a time as possible. Like you, I also started with fresh substrate. If done right, I don't think there is much risk of a crash because it is almost as if you are doing a huge water change and changing out the glass.