take a look at the saiga-12. they really kick ass. reliable AK action (piston operated, rotating bolt), high cap 10 round magazines, and only like 400$ for a stock sporter model. cant beat it with a stick.
has an adjustable gas system to run reliably with anything from light target loads, to 3" slugs. no inertia system to get jammed up with extra weight, and a much more efficient gas system than an 11-87 (dont get me started on that POS, worst gun I have ever owned). plenty of places to get it converted to "evil" assault weapon style for around 300$. or do it yourself pretty easy, for even cheaper.
not only is it the coolest looking gun I have ever owned, its reliable as shit. and only about 100$ more than a 590, and much cheaper than the benelli. check out the saiga-12.com forum for all the info and pics you need to make the right decision.
btw, the 590 has a 20" barrel, you should get an 18" barrel for a HD gun, it will handle better in close quarters. the winchester 1300 pump w/18" bbl (defender model) holds 1 more shell than the mossberg 500 w/18" bbl. my freinds 1300 has run great ever since he bought it. if you want a pump look up the winchester, the ergonomics and price are almost identical to the mossberg.