Bill,
I would look for a good, used 20GA Remington 870 on gunbroker.com. Just make sure you get a 3-day inspection clause so you can clean and inspect the bore. IT should be "perfect" with no pitting. A good price would be $250.
Now a "sleeper" 20GA shotgun out there is a Charles Daley 20GA. They sometimes recoil a bit harder than other 20GAs but they flat out get the pattern out there!
Since Charles Daley went out of business, you might be able to pick one up for a steal somewhere.

Finally, if you want a little something "different," look around for a Winchester model 12 20GA. The barrel could be threaded for screw-in choke of your liking. Lots of guys do this for card shooting shotguns but largely, the turkey hunting fraternity overlooks customizing older shotguns with new barrels. Mistake IMO.
