RE: $600 to spend on a shotgun?
Bass Pro has the Remington 11-87 on sale for $699 right now and is two toned in black and camo. You might want to check it out. As far as shotguns go, it would either have to be a Remington or a Bennelli for me.
They also have the Benelli Super Nova for $549 on sale in all camo but I do not know if it is semi-auto or not?