And, since you asked ......in my humble opinion if you are looking for a home defense shotgun for less than $500, you can't go wrong with one of these:
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I bought mine new for less than $300 two years ago. Plan on $350-400 now. If you really plan to use it for home defense, hang a sidesaddle and maybe a light on it and call it done. No need for any more tacti-cool junk to get in the way. Spend the cash you would spend on useless accessories on ammo instead and learn to use your new gun.
Find a tactical shotgun match in your area and learn to operate your gun under stress in a simulated combat environment. It's similar to an IDPA match, except for shotguns instead of handguns. If you ever have a chance to shoot a tactical match you will understand why I believe in keeping accessories to a minimum on a gun you trust your life to. You don't need a sling that will hang up on a piece of furniture and jerk the gun out of your hands, or a heat shield that comes loose due to recoil and jams up the forearm rendering your gun useless. Been there, done that as they say.
You might also look for used 870P or an 870 Wingmaster and add an 18" barrel and a two round mag extension. Both can be found in this same price range. I have owned a truck load of shotguns over the years, some expensive and some not...I'm a shotgun junkie.
IMHO , their is no better value than a Remington 870 Express. Take care of it and it'll last two lifetimes.