This is a question that I should know the answer to, but what is the difference between the TEIN S-Tech's and the Eibach Pro springs? The Eibach's are more expensive, so the only thing I can think of is that they would be made out of a different material (for as much of a price difference as there is between the two). Also, I found some RS-R springs, but I have never heard of them. Any thoughts?