If I were going to get a slug gunI would get a dedicated slug gun. One of the bolts listed above if you can find one or a NEF ultra slug hunter and the new Ithica deer slayer III looks very interesting. Most of the dedicated slug guns are going to have a much thicker, heavier, and stiffer barrel which will be permanently attached to the receiver making them much more apt to be more accurate.

Of the ones you listed it would be the Beretta. But you said the price was an issue with the Benelli. The extreme 2 is right there with it in price.

Another one to look at is the Benelli Super Nova. In a pump this would be my choice.