That is a lot money for suspension... Especially Tien suspension... I know I currently have Tein Basic coilover in the front, but I paid about $100 for the pair (used).
Even at that price, some suspension gurus tell me that I overpaid and that EVO stock KYB struts were better. I am not sure I trust that judgement, but I would think twice before spending over $1k for Tein suspension...
Can you get a part number for the adjustable rear spring sleeve? I might inquire about it directly from Tein.