Something else to consider is looking at your game laws. Some places you have to have a plugged gun and having 7 shots in your gun isnt agood thing to have if your not supposed to have that many. Fines fines fines! I have a Remington 870 Express Magnum Combo and i LOVE IT. Ive had it for a year now and its never failed me. I shot my first deer with and at about 150 yards! Its a combo so it comes with a slug barrel and a "bird"/ Buck shot barrel. It only cost me about $300 to so its a good deal all around. That marine 870 your looking at is more of a police/ home defence gun. I would highly change your thoughs on getting that firearm!
Best wishes, Jake