What you have to ask yourself is, how committed are you and how diligent are you with your maintenance? While saltwater has become much easier due to the vast amounts of information available, it's not something you want to be lazy about like so many are with freshwater, mainly because they're able to get away with it and it becomes bad habits. What I always recommend for tanks roughly your size and larger regarding filtration are a wet/dry filter, protein skimmer, canister filter, u.v. sterilizer, and depending upon the temperature the room gets where you live, you might need a chiller. With that being said, sounds like you want to keep it a little more basic, so what I would get along with your canister filter is a hang on protein skimmer, a strong air pump, and a heater (which you probably already have). That will cover you for a basic set up scenario with filtration, I'm sure you're already familiar with crushed coral or sand, decorations designed for saltwater, get a good reliable test kit (ph, alk, amon, nitrite, nitrate), hydrometer, and with all do respect to the above member, DO NOT GET an auto top off, just something you absolutely do not need for a beginners set up, once you get a bit more experienced and do have a wet/dry filter, then you can consider that. Their's plenty of options you can get but for now let's keep it simple, also keep FISH ONLY, DO NOT start dabbling into invertebrates and crustaceans, there will come a time where you'll have to medicate your aquarium and most meds will kill these guys. So stick with fish that are durable and stay small (royal gramma, flame hawk, cardinal fish, clownfish, gobies, ect ect), I would stay away from damsels, they're beautiful but very territorial, you actually have room for the related chromis, but be very selective and ask questions. As one of the other members suggested, PLEASE DO SOME RESEARCH, don't just try to wing it and waste money, time, and loss of fish, you'll enjoy it so much more.
