Right under the FinalGather (rollout) there is the Sampling Quality rollout. In there change your min samples to 0 and max to 2. For the filter type I like Mitchell instead of Box. really nice anti-aliasing.

You might note. that when you tern on FG or change the Sampling Quality that the first rollout with Quality on it changes to custom. If you change that back to draft or any other it changes the settings you have made below. This is why I suggest just leaving the quality alone and set the rest to your liking.