Yep , for USDM it seems that only the STI gets a LSD in the front.
Phantom grip, Quaiffe and this Subaru helical :
http://www.rallispec.com/prod_diff.htm
which i'm guessing may be from JDM cars ?
I'm leaning heavily towards a Helical as they are more street friendly and less maintenance (or known if the ad is correct)