None of the below options are less worthwhile than the others, it just depends how much time, effort, or money you want to put into it.
Lets be realistic, all you need is something that will always go bang and feed ammo reliably. If that's all you want, get whatever pump is cheapest that still works. My first HD scattergun was an old, beat up, $100 gunshow special stevens model 620, that I chopped up and had no qualms grabbing for bumps in the night.
If all you want is an extended magazine and plain bead sights on a proven reliable pump, get a 500.
If you want a pistol grip (because of the location of the safety) and/or really want to tacti-cool it out, get an 870. I wanted another HD gun because I could, and wanted to upgrade my options from the trusty 620 I'd had in the bedroom for years. After reading a bunch and planning out exactly what I wanted,
I built this.
Again, don't let anyone tell you that what you have isn't sufficient. If you can hit what you need to, when you need to, without fail, anything else is icing on the cake.