should be plenty to find in that price range. two things:
1) gas over inertia~ coming from the Maverick pump, either will be an improvement, but take and see what you like/don't like about either system. It will likely make a difference to you over time, so shoot a couple from friends if you can.
2) why used? If it's street cred, then you're in the right ball park, may want to increase $100. For $700/$800 you could be looking at new and have better selection: i.e. gas vs inertia, barrel length, finish, etc. AND not have to deal with the last owner's bad habits, lost choke tubes, etc. Example:
http://www.weatherby.com/product/shotguns/sa_08/sa08_synthetic