For trap shooting pump or semi doesn't really matters but for hunting I think a semi would have an edge for quick follow up shot especially you have mentioned hunting waterfowls and for that reason I will pick either the Stoeger M3500 ( little over your budget around $600ish but well worth the investment ) but if you are recoil sensitive then the gas operate Baikal MP153 aka Remmy SPR453 can't be beat as they should all 2 3/4 to 3 1/2 hunting load without issue.
I know many likes the Mossy 930 / 935 but don't have first hand experience on it.
I know many have seen this but I can't resist to post it again
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And the 50,000 rounds non-stop test in Italy
www.shotgunworld.com/bbs/viewtopic.php?f=83&t=69680
[youtube]YwL_JEsJ1b4[/youtube]