Who should I start at QB this week??

I have Peyton Manning and Ben Rothlisberger. I am thinking that if Indy gets a good lead that Dungy will sit Manning which killed me a couple of weeks ago. But I am pretty sure Ben will play the whole game since they are still trying to get in the playoffs plus he is playing St. Louis and they are horrible against the p. What do you guys think?? I also have Derek Anderson against Cincy but he has cooled of late and I don't look for him to rebound this week. But the best game of his career was against Cincy earlier in the season. Help, to many QB's!!!!!