I'm trying to make a decision on suspension parts for my car as well. Like a lot of XIers, I'm looking for a modest drop and tightening things up without frigging up the frontend too much. After lots of research and chatting with a few board members here, I'm somewhere between Koni sports + Eibach prokit or Bilstein Sports + Eibach prokit.
Shox.com has a set of Konis on for $551, and Turner Motorsports has Bilsteins for $440. You should be able to pick up Eibachs for around $250.