I need to keep at least 4 players from last year. Who should I keep?

I know I'm keeping Manny Ramirez and Prince Fielder, but can't decide on 2 more from the following: Alexei Ramirez, Carlos Delgado, Joey Votto, Troy Tulowitzki, Chien-Ming Wang, and Aaron Harang. I can keep up to 6, but with this lot I thought I would be better off keeping the minimum and getting 2 extra draft picks. Ideas?