I'm also a big fan of the shrimp paste noodle dish at Nha Trang. However, Huong Viet, on what I think is the south side of the parking lot, a few doors down from Than Son Tofu, serves consistently good food from its large menu. Their cha gio set the standard, and they grill meats to perfection.
Than Son Tofu's bubble drinks are pretty good (some places use a powdered mix that is nasty) and get a dollar's worth of each of the fried tofus to munch on your way home.
My favorite meal is at Nha Trang, #7-8 inside the Saigon East interior corridor not visible from the parking lot.
Get the noodle dish with shrimp paste "in the shape of worms (according to the menu)." This is a soup. Also get their specialty, garden rolls with grilled pork, I think the #7 appetizer, but just ask - there is a picture on the menu. They also have very good roast quail and minced clams.
For carryout: at Than Son Tofu, they make a vegetable cake, but they run out quickly. It is normally to the left of the fried tofu in aluminum trays.