You can't go wrong with an 870. I absolutely love mine. I went the expensive route with a Vang Comp Systems 870. Even with an 18.5" barrel, I can shoot trap.
One (possibly bad) thing to note. Many of the 870s that are marketed as hunting shotguns (including the Express) have a little detent in the magazine tube, making it difficult, but not impossible, to install and use a mag tube extension. CHECK YOURS BEFORE YOU BUY IT. One customer came in with an 870 Express that he wanted to convert from a long barrel hunting shotgun to an 18.5" defense gun. We had to take out the damn "nipple" with a dremel tool, and now he has a nice 1/4" hole in his mag tube.
The only two 870 models I know of that do not have this detent are the 870 Police, and the 870 Express Defense (which has the extension already installed from the factory).