Ooohhh... I would..
have a huge tank that wrapped around a large room. It would be a freshwater community tank. In the center of the room I would have about a 55G SW hex tank.
Somewhere else on the property there would be a 1000G tank the size of a large room. This would also be freshwater and include irridescent sharks, channel cats, red-tailed cats, gars, and many other large fish.
I also would have a 100G African cichlid tank.
I would have a huge saltwater tank that takes up a wall in the living room. Here comes the expensive part, a service that did all the work keeping up a beautiful salt water tank.