turbo 6 bangers post here

Ok, I'm planning my exhaust right now and I'm trying to figure out what size piping I should do (I'm eventually going turbo and I don't want to redo my exhaust) and its between 2.25 and 2.5". Also, I'm going to use a Magnaflow glasspack and I wonder if I should get one glasspack and Y it off after it, or Y it and go with 2 glasspacks (one for each pipe since Im having dual outlets). If anyone has any insight on this, please let me know. Thanks!