There are probably some very impressive setups out there that aren't publicized for whatever reason. I've heard of a few home reef tanks in my area from aquarium maintenance companies that are in the 1,000s of gallons and cost somewhere in the 6 figures to set up, but they won't divulge much more than that.
But one tank that comes to mind is David Saxby's in England. It's something like 1500 gallons and has a nice writeup in Ultimate Marine Aquariums. That system is completely set up with the best of the best.
There are also several impressive home reefs in Germany that I've seen on the internet.