Lowering Springs

Damian,
Looking for some advice on lowering springs as totally confused after reading loads of threads. I have an A3 S Line 170TDI on a 57 plate.
Now I am looking at dropping it about 20-25mm and getting a better ride. The current S Line springs are too harsh for the roads round my way.
From what I understand, the S Line is already lower than the SE and Sport.
Question is what drop do i need to lower from S Line to go another 20-25mm and which in your opinion are the best springs to go with? From reading the threads it looks like a toss up between H&R and Eibach. I dont however want it to have the front sloping down. Ideally keep it as is but just 20- 25mm lower all round.
Hope all this nonsense reads well and you can help me out.
Regards
Iain

Damian
Following on from my post I have spent hours on the net researching springs for my car.What is your opinion on the Vogtland springs? Have you sold many of them? They appear to be made by eibach and will give the exact drop I am looking for. Cheers. Iain