I am by no means an expert, but I do know a thing or two in regard to your post. Generally, a shotgun set up for home defense is not particularly well suited to game hunting. A home defense shotgun needs to be as short as is legal to possess so that you can manuver with it in confined spaces. A game hunting shotgun needs to have a full length barrel in order toget as much velocity as possible from the cartrigde fired.
A Remington 870 is a fine shotgun and can be found for very reasonable prices. I am a fan of Mossberg shotguns because they work and function as well as the higher end guns and are inexpensive enough that if I drop one over the side of my boat, I will not have that horrible feeling of loosing a $1000 investment.
You may want to consider getting an 870 or 590 with an additional barrel. One cut to minimum legal length for home defense, and one that is full length with interchageable chokes for field use. The again, getting one of each for less than $400 total should not be a problem.