If you had to choose your poison, I think you’re right in wanting to stop Brown and the passing game, first.
Pretty sure Belichick has a gameplan in the HOF where they pretty much did exactly what you’re suggesting, where Thurman Thomas had 135 yds and a touchdown, but they limited the strong passing attack, or at least didn’t get beat by it.
Of course, one can argue what Bell having a “great game” really means to them, but it would make sense that Belichick would try and limit Brown, thus forcing the Steelers to march down the field in an attempt to beat us. I read an article stating that they’re the 25th ranked RZ team, offensively-speaking, and that as a team, they currently have the 5th lowest YPC average at 3.7 (Bell has a 3.9 average).