I'll echo what Ganef said by recommending an 870.
It's THE shotgun.
I steer clear of Mossbergs because of past QC issues and the fact that they are apparently more difficult (read: Pain in the ASS!) to take down and maintain.
I'm not the type of guy that does stuff because "I read it on the internet" or "so and so said they're gay" but when it comes to guns, I pay attention to guys who know what they're talking about. The combination of said folks telling me Mossbergs were pieces of shit, and my own personal experiences (quite sterling, I might add) with the 870 lead me to buy one for my own use.
Regardless of whether or not you're going to add accessories, rest assured that any accessory that is made for shotguns is made for the 870. Mossberg isn't far behind, but behind it is.
If you can find one, a "Remington 870 Home Defense" get's my vote. It'll run you around 350 locally, but has some extra features that make it a better value than the standard 870 Express. It includes a mag extension that brings capacity (with 2 3/4" shells) up to 7+1 and has synthetic furniture.
It's capable of firing 3" Magnum loads, however unpleasant they may be, and has unfalteringly fired any loads I can get my hands on so far.
For your home, I'd recommend a light of some sort, whatever you feel comfortable with, just keep in mind that you can't hit something if you can't see it.
I'll defer any legal speak to our resident lawyers to discuss ad nauseum, but I'm pretty sure you can't shoot some dude in the parking lot for breaking into your car in an apt complex.
One more thing, Benellis are nice, but semi-auto shotguns severly limit the loads that can be cycled. 870 Pump action never fails.