Lots of good info, but not 100% accurate.
The DCCD (Driver Controlled Center Differential) only alters the torque bias split between the front and rear axles. It has nothing to do with a front LSD or rear LSD. Those are independent items. This is only the center diff, sending power to the front or rear.
For example an 05 STi has a normal bias of 35% driven power going to the front wheels and 65% going to the rear. With a DCCD, you can "LOCK" the ratio to 50-50% if you want. The electronics involved in auto-mode can make on the fly adjustment of this split based on what information it receives from the sensors.
As for LSDs. They are a no brainer when it comes to putting the power down to the pavement. Without a locked front or rear diff, you will be a "one-wheel-wonder" that everyone has seen at the stoplights at icy intersections. Being that it's a Subaru, you don't want to be that guy.