If you get a 590, MAKE SURE THE MAG SPRING is not defective. I got a used one and the spring kinked every time the tube was loaded. I found out too late that it was a problem with LOTS of 590s. That's probably why a near new shotgun went for so comapratively little. The shop didn't say a thing about the problem with that particular weapon, or 590s in general.
A Wolff spring replacement solved the problem.
Oh, yeah, my 590 has "an Accessory Lug". I hang a M7 Conetta on it.