The Savage 311 type is probably the closest one can get to an 870 in a SxS as they are inexpensive, common, relatively rugged and simple to repair. Their negatives are clunkiness and most often being found in Mod/Full- at least in this region. I've used one in 16 ga for my sporting clays league the last two years with little problem.
The next step up will run at least double the Savage and more like triple or more. These would be various Spanish guns, Japanese guns like the SKB, some German/Belgian/French guns (especially guild guns), and American guns like Winchester, Ithaca, LeFever, and Parker. These will cost more as mentioned, may be in a lesser condition, parts could be an issue due to age or uniqueness, and they might be stocked differently due to a different way of shooting if one is looking at an older gun. I've owned a couple of German SxS as well as an Ithaca and a Parker. I did not care for how they fit and the cost of a new stock was prohibitive to me so they went down the road.
The next step will be over a grand and often well over. They will all be decent and one will have to decide for themselves if the cost justifies the use.
