Another option you might want to consider (depending on how much you like to tinker) is to go and look for an old, beat up wingmaster. These can typically be had at about 50% of the cost of a new 870 security, but you will have to then add the 2 round magazine extension and possibly buck the barrel down to 18.5 inches in length. Why would you go this route? In my opinion, the older wingmasters are much better made than the current 870 expresses. I did not believe this when I first heard it, as I was the proud owner of a brand new 870 express, however now many years (and many 870s) later, when I want to add an 870 to the collection it will always be one of those old diamonds in the rough (the only thing that will be rough about it will be the finish...everything else is better!)
Take care,
Brobee