Umi has a giant sushi train in the middle of it's restaurant in Darling Quarter. It's a very busy night and a bit of a wait but I think worthwhile.
Their udon dishes are tasty and very reasonably priced. There's the chicken katsu udon (with egg, splashes of seaweed, tempura flakes) and I also ordered the beef teriyaki spinach udon dish (with the same trimmings as the first udon). The sushi plates are good and consistent but I suggest you do a combination of main/sushi plates.