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Found one @ The Gun Source for a little over $300... Apparently I can buy online, ship to a local dealer, and pay the dealer $25 bucks to do the paperwork.
An 870 is an 870, so don't be afraid to shop around. I've used Gunbroker before, and there are some good deals to be had there.
Be aware that some of the less-expensive, entry-level 870s are Express Tactical models that are built on receivers with the long magazine tubes. If you're looking for an 870 with which you'll be able to change barrels for different roles, these models should be avoided (and chances are, employees at big box stores won't know the difference).