I read let's talk diff thread a few time on tuners. From what I got rear diff is the first upgrade, and the bets handling mod according to some, one should make. As stated it provides a more neutral balance to the car (less understeer) and really helps to throttle steer and rotate the car around corners. The two other are a bit more complicated... If you upgrade the front in theory the center diff shouldn't work as much. The only problem I have found is the most popular front diff offered are 1.5 or 2 way as kaaz and Quaife. This produces off throttle understeer which is really counter intuitive ( imagine arriving at a corner a bit to fast, letting go the throttle and suddenly bam understeer the car can't turn) . The ideal front diff IMHO would be something like what was recently sold here...:( a 1 way meaning it's locking on throttle only. Center LSD diff are usually even more expansive and arguably could be the last one to be upgraded. Not sure that helps.