The Nova is nice, but the safety is in a different place (in front of the trigger) compared to many guns (even the Benelli automatics), so that is hard for me to get used to. If you haven't shot a lot of other guns, that wouldn't matter. I think they are a bit more expensive now -- mine was 400 with the camo finish. The grip feels fat compared to the slimmer Remington. But they are designed for speed and are accurate, and certainly have a newer and intimidating appearance.
I think the 870 Express is the best deal -- its the same action as all of the 870s, just a less fancy trim level. We've used 870's for years, dropping them in lakes, slinging them off the camper top going down the highway, and who knows what else. They hold up great.
I have an older mossberg 835, and it's unbeatable for turkey hunting. They were traditionally a cheaper brand, but have really stepped up a notch in the past 10 or 15 years.
I would say try those three (and maybe a winchester?)and see which suits you best. Try to get them out and shoot a few clays or something if you can. You can't go wrong with any of them IMO.