Hello monsi, and welcom to cruise-chat;
Neil's advice is excellent. A good travel agent is your best source of information--one who knows cruising.
Let me just say, I have been on both clases of ships doing the Voyage of the Glaciers, and they are designed in such a way that there are virtually no bad cabins. You might want to avoid inside cabins on Plaza and Emerald decks as they are either below or above showrooms; but there are only a handful of these cabins; and even so, I have never heard anybody complain about noise--not even near elevator foyers.
So I think your best choice for value would be a gurantee booking in the least expensive catagory--and also your best chance for an upgrade.
Whichever way you go, have a wonderful cruise.