I like the 870s but I am unsure of the differences in models available. I am not opposed to a mossberg either. I really like the look of the 590a1 tactical, too. I am just looking for advice on pricing, reliability, and ease of modifications. Also, I am seeing shotguns with barrels shorter than 18.5" on the board...is there a different permit required for these. Since this is a home defense shotgun, I want it to be compact as possible. Thanks.