So many choices, and so few of them are actually bad!

One of the few times in your life you're going to be in that situation

Try one of these: Baikal MP-153.
Tough, cheap autoloader, shoots 3.5 shells.

But Remy 870 is a fantastic gun. I have three now, and I used to a few more. So is a Mossy 500 and a Mossy 835.

I could talk merits of each, and many others, for hours.

Handle and shoot as many of them as possible and see which ones you like best.

Then see what deals are available.

Your choice may become obvious at that point.