What do you mean by subtropical? A typical reef tank runs at 78 F or so. Are you looking at setting up a more temperate tank in the 60’s. If so, yes, there are inverts, corals and fish that can be kept in those temperatures….just look at the stuff you find in Southern California waters. If I lived there I’d be pulling stuff out of the ocean to stock my temperate tank. Anemones all over the place, small Garibaldi fish and maybe some small kelp plants, mushrooms, limpets and much more.
EDIT TO ADD: You will have to run a chiller to maintain the tank at these cooler temperatures. Also, check out any of the many aquariums in California. Most have indigenous species tanks. I was just at Birch Aquarium in La Jolla....nice selection of local stuff.
