cliffnotes of what everyone's bout to tell you. get the base for turbocharging/supercharging, nitrous. get the SH for mild modifications or no modifications at all. wheels, side skirts, courtesy lights, leather shift knob, standard spoiler, ATTS are what differentiate the SH from the base. SEARCH SEARCH SEARCH SEARCH!!! SH is 88lbs heavier. whether the ATTS is worth it is totaly up to you depending on your driving style and intentions for your car. SS is the sportshift, available only in the base model. ATTS (Active Torque Transfer System): torque is transfered to the out wheel in a turn thus givin improved handling. it's not perfect but it's no gimic either. i have the SH, it's boosted, lowered and i'm happy.