it's been awhile for me since I last sold my '08 STi but why would you need new shocks/struts? are the origs going out? if they are then it's prob a good idea to do both at the same time. car seems fairly new, unless it's like a high mileage unit, so I wouldn't bother with new bushings etc. I thought the eibachs only lowers the car like 3/4" if even that much? I don't think that small of a drop would effect your OEM struts/shocks. just make sure to get a proper alignment when done.