I also have an 870 Express. I installed a Remington 20" barrel with rifle sights, a Limbsaver butt pad, and a Choate magazine extension. I keep it fully loaded with one in the chamber and the safety on.
On a side note, I found a little rinktum that you can fasten to your door jamb on the handle side of the door that will prevent little ones from opening the door. I found it at Lowes in the door hardware section. I just looked on their website, but I couldn't find a link to it, and there isn't a name on the rinktum. It looks like a hinge, and works by pushing up on one half of it and folding it over like a hinge, which allows you to open the door. Then when you want to keep the little ones out, you fold it back over the wood part of the door and it drops down blocking the door. Works pretty slick and keeps the granddaughters away from the shotgun. I'll see if I can attach a picture to this post.