I'm just a novice, but I've owned a couple of Mossberg 500', and a Maverick 88. Good shotguns that would meet your criteria, IMO. I do think the 6 shot models are a little more handy than the 8 shot models.
My old Remington 870 Wingmaster with a 18 1/2 " slug barrel has an action that is silk smooth and it can pump out 5 shots of buckshot faster than you would think possible. Some people say a good pump shotgun in the right hands is as fast as a semi-auto shot gun. I am not sure about that but I do know that 5 blasts of 12 gauge 00 BUCKSHOT IN 3 OR 4 SECONDS is pretty impressive and at close range will stop about anyone or anything most of us will ever encounter. My vote is for a Rem 870 with slug barrel.