I suggest (in no particular order) the 11-87 [easily in your price bracket] the browning gold or silver line and the beretta AL390 or AL391. The last two may be hard to find at the $800 mark but it should be possible. I haven't checked prices on them ever but on the net I've found a few going for the mid 700s.

Now, if you aren't opposed to a pump the remington 870 wingmaster or Browning BPS will never fail you and make beautiful field companions...and there's that added comfort of knowing it will cycle regardless of how nasty things get.