I've talked to a lot of folks who shoot the Stoeger 2000 shotgun. It's a fine gun that's capable of shooting excellent patterns. The addition of an after-market turkey choke can certainly help its performance however.
I recommend the SSX for that shotgun. http://allaboutshooting.com/product_info.php?cPath=23&products_id=79
It is very reasonably priced for a premium quality turkey choke that is rated for all lead and tungsten-based shot. It has excellent internal geometry and delivers dense, even patterns with a variety of shotshells.
That choke with the 3" Winchester HV or Winchester XRHD or Hevi-13 shotshells will produce some great turkey killing patterns.