Start with a Remington Super Full. I've tried them all and this is one of those cases where the least expensive options can also be one of the best performers.
I've got 2 870's that I use for turkey and both of them love this choke. Also had good luck with the Primos Tightwad.
Lots of good options out there for ammo but I started patterning the Longbeard XR's (I bought the 6's) and they've looked really good on paper.
