OK, found a bunch of pics of both my newer 870 with a Choate 5 rd extended tube and the 590. 590 has sidesaddle, buttstock shellholder and slings plus tac light, and a mag tube follower upgrade. Came with the heat shield too, most 590's come with them.
if you're wanting an AR style stock, go with an 870, with the mossberg's tang safety, it will be tough to manipulate, the 870 has a crossbolt safety that is much easier to work with a pistol grip style buttstock.
my tac light:
and a full photo of two of my shotty's:
don't forget to choose good ammo too, I would recommend something like Federal 12g 2 3/4" shells in #4 buck, won't over penetrate too bad and has either 27 or 34 pellets
don't use birdshot either, I hate when I hear stories like 'homeowner shoots intruder twice with 12 gauge, then bad guy left...' You tag someone with buckshot a few times at in your home distances, they're not leaving until the coroner shows up.