So this past weekend my wife and I did this upgrade. Thought I'd share the experience as I have read a lot of people asking about upgrading.
So, this is how I did the upgrade.
Couple days before I mixed up saltwater, I have a 64 gallon recycling bin and 32 gallon trash bin.
The morning of the move I started by filling a old 55 gallon tank with the tank water, I added a heater and a powerhead. From there I began draining the tank into 40 gallon rubbermaid bin. While the bin was filling I removed all of the coral moving it into the 55 gallon fish tank. Once the bin was filled ~60%, I moved the draining to a 32 gallon trash can and removed all of the live rock (~160lb) into the rubbermaid bin.
Once all the rock was out I caught the fish and they went into the 55 with the coral. Once the 32 gallon trash bin was filled I finished draining the tank into yet another 32 gallon trash bin.
Now with all of the water out we moved the 155 out of the way, and slid the 200 gallon into place. We shimmed it level and began putting some of the fresh saltwater back into the tank with the heater to bring the water temp up. At this point we began moving the rock into the new tank along with 50lb of previously bleached and acid soaked Figi dry rock. As one container emptied we moved the pump to the next and kept filling the tank (we actually had make additional water during the move)
After all the water was in place we tested out the pumps, realized I needed a ball valve in place so a trip to lowes (they didn't have what we needed) followed by Home Depot was made. The coral was put into the new tank, then the fish.
Here's a picture of the finished tank.
It's been 3 days now, the water parameters are fine, fish, coral and invertebrates all look healthy.
I apologize if this was a little long winded, but hopefully it helps someone.