In Santo Domingo there are much better choices for actually getting laid, so the massage place is really to have a good sensual experience with a nice girl for a reasonable price. There are some clubs on Maximo Gomez itself but the houses are on the back streets, discretely mixed in with a normal and safe working-class neighborhood. These are brothels with a wide range of girls. I have never done it, since I don't want anyone to be able to trace my adventures, but I have seen plenty of prostitutes with Europeans in the elevators of fancy hotels, and girls that come in to the lobby phones, call upstairs, and then go up. They show ID to the desk.
Some places are more expensive still.
Some of these places advertise in the Yellow Pages, but the best way to get introduced to the scene, even if you speak Spanish, is to get a taxi driver to drive you around. She was very tender and loving, with good technique and a genuine desire to please. It was like making love to a young Latina bride with no sexual inhibitions. Obviously, YMMV, and I have seen some girls in these places who look plenty bored. My final advice is on the street scene.