For a first timer, I always recomend going with the biggest tank you can--the 35, in your case. While you can go small, there are several problems facing a newbie. First, small tanks are not as stable. Larger tanks won't have fluctuations in salinity daily--evaporation in a small tank can kill. Second, cycling a large tank is easier, because you have more room for bacteria to grow, and a larger volume of water to dilute spikes. Third, one of the biggest problems with SW is buying an animal that will far exceed the capacity of the tank. Bad enough when you're dealing with a 55, but outrageous when you're taking about something less than 2 cubic feet.
So, yep, there are some tiny tanks out there. They look cool, but they require daily attention, and careful planning. For a newbie, something a little more forgiving is more likely to result in a happy hobbyist.