I have no idea about a comp gun,but I have a Mossberg 835 ultimag and love it. It will handle 3 1/2" shells and I have a short 24" turkey barrel, 30" regular barrel both of which take the same choke tubes and also have a rifled slug barrel for it as well. It is the best all round hunting gun i have owned.
I don't think you can go wrong with a good old 870!
I bought an 870 combo, came with a 20 inch rifled slug barrel and a 26 inch field barrel. I think I paid 300 after a mail in rebate from Remy. For fun I have tried slug out of the rifled barrel out to 100 yards and was surprised how accurate. I also keep the rifled barrel on for home defense. Its short enough and if i ever have to use it I doubt i'll care if i messed up the rifling. Use the field barrel for shooting clays, crows etc. For around 300 you can have a gun that serves 3 purposes.
This is a PSA:
The OP asked about a semi. 870s, 1300s, 835s, and pretty much everything else mentioned other then the 1100 is a pump.
I'm not saying anything bad about pumps, but he asked about a semi.