I keep my temps at 79, but after reading a article in the reef annual, i'm thinking to lower it maybe to 76.It seems the coral reefs are average of about 82/83 but the fish move in and out of the reefs and prefer cooler temps of mid 70s during the day and mid to upper 60s at night.
We keep our tanks at 80+ only because of the diversity of corals found at the equater (spelling). Corals are not only found there. I think some (or most) will survive and thrive at cooler temps.
At 79 deg. my SPS corals are growing at a good rate. At 76 they may slow down a bit but I feel they will still thrive.
I will lower it only because I want to also think of my fish. The study was about keeping fish alive longer in your tank. In the wild they live longer and it is believed higher temps shorten the lives. They are more aggesive, eat more, ect... Lower temps slow them down.
HTH