So, your plan is a third tank, not transferring corals from your smaller to the 40B? If that's the case, I would probably do something more species specific. I keep dumping money into one tank, but there are two other tanks I would love to set up if I had the time and wife's permission.
One would be a non-photosynthetic tank with sponges, gorgonians, sun-corals. I LOVE those tanks. But, they require a lot of filtration to fight the fact that they require a LOT of food. Filter feeders. Go figure.
The other idea I would love to pursue would be a species specific tank with a frog-fish and lots of ornamental algeas and mangroves. Or A pipe-fish tank with similar plants and maybe some softies. Those would be more accessible, easier to keep ( I'm only assuming ), and cheaper to set up (again...assuming). I would have to do more research, maybe these tanks are more demanding than I would think, but you wouldn't be as concerned about excess algae growth, the ugliness is part of the fun. You just want to make sure the fish have healthy living conditions.
There's my two cents. When do we start?
very excited... 
