Your site is a great initiative.
AH’s dominance in Amsterdam is a HUGE annoyance. Two years ago I filed a complaint on this matter at the Dutch fair competition authority (NMA), which was turned away for the fact that AH obtained its position in Amsterdam due to ‘good entrepreneurship’. Of course that’s a nonsense argument, but it gives a good insight in how the government deals with it. Change in the Amsterdam supermarkets business will have to come from the bottom-up, and therefore you have my full support!
(edit: please see the comments for the whole reply from NMA, in Dutch)