I just transferred a pretty full 40g. SPS system to a 93g. cube last Sunday. I "seasoned" the new cube by numerous water changes from the old display. There was a few fish and some rock in the new tank. I was very nervous about this move, but needed to do it, as you can see.
The actual transfer took about 5 or 6 hours and included moving water, corals, fish and rock into bins. I then moved the tank out and the new one into the same position(after removing the water, rock and fish into holding bin, which then got moved back into the tank). Basically everything from the old tank got moved back into the new tank. This included quite a bit of water and the same pumps, skimmer and sump. I really wanted to replicate/replace as much of the bacterial base of the old system in the new.
I will slowly replace equipment with new stuff, including a new larger sump. But I am in no hurry because I am still nervous and am hedging my bets as much as possible.