For that special occasion, why not try Shiki's Japanese Restaurant situated in the Hyatt Hotel, North Terrace, City.
The meal is expensive but the food is really high quality and is cooked tepanyaki style right in front of you. Setting placements are about 10 people per booking so if you are only going as a couple, you will be sitting with other people unless you request a private table. That's all the fun of it though.
The set meals range from $75 per head plus drinks.
We will always go here now when we have a special occasion.