I would listed Santouka as the best in the Down town area. As a reference, I've been to Kenzo, Kinton, Momofuku, Ramen Raijin, Sansotei, Touhenboku and Ryu's. In order to have a filling stomach, I usually pick the Soi broth ramen with a grilled salmon rice combo (#22). It is always good to have some rice at the end.
Their service is quick but kinda rushing you at the same time. This is the reason I gave them a four stars instead of a five.