The actual brand of gun is something that you are probably going to have to ultimately choose on your own. I think all the guns mentioned will serve you well. I personally have no problems with the Mossbergs...although they are definitely not as "purty" as some others.

Have you ruled out a 10ga? I've seen them in action on turkeys...and was absolutely floored. I know they're awesone with steel shot, too. After patterning and shooting a ton of shotguns...those in 10 ga just seem to be a little more consistent. In my opinion, the larger casing allows for better balance between powder and shot in those heavy loads.