Sorry if it's off-topic, but what's wrong with Eden Park's position (as opposed to it being stupidly overbuilt right now)? Right next to a train station and a cozy inner-suburb centre with lots of pubs. I'm not impressed by any argument involving parking because Aucklanders should GTFO of their cars. In contrast, the waterfront has nothing near it but yuppie apartments and car parking (Auckland's answer to Wellington's logs).
Its in the middle of suburbia stopping concerts etc. A waterfront stadium would not have these problems and would also be easier to get to for people on the shore, out west, out east and down south.
Visit the Mile High Stadium or Pepsi Centre in Denver or Millenium Stadium in Cardiff to really expereince what its like to not have to worry about NIMBYs or noise polution/control.