RE: auto loader
A gun in 3" is enough for duck hunting. 3 1/2" is fine also if That's what you prefer. I only have experince with three of your five. The C.D. is the lowest price of them all. Some have had a lot of problems, while others don't. The C.D. needs to be kept cleaner the most gas semi-auto's. I've shot about 100 round thru a 912. I have not whitnessed any problems wih this gun. I do not hunt with It's owner, so I can't comment on it's field performance. It, like he Beretta Xtrema are "big" guns. One of my buddies had the Remington. It's gone because of the mulitple problems. I have heard a lot of good things about the Stoeger 2000. I think the jury is still out on the Mossberg (too new).
I know you did'nt ask but, If I may. I'd like to suggest a couple of different ones that I have a lot of expenince with. All are semi-auto's in 2 3/4"-3" and go for about $550.00 in the full camo models. Beretta "ES 100/Pintail", Franchi "612", and Weatherby "SAS".
Of the five you listed my picks would be in this order. Stoeger, Franchi, Mossberg, Charles Daly, and Remington.