Im going to lower the car soon using 40mm koni springs(not bgot the springs -yet)

Big question is do i buy the koni springs or do i buy some genuine s-line ones off e-bay?

s-line ones state ''will lower the se model by 20mm
koni state upto 40mm.

Also the s-line ones for sale are from a 2.0 tdi-s-line (2005) will the 2005 ones fit 2002 model car?

my car is not even an ''se'' model its the standard 2002 b6 a4 tdi.
ive been told lowering with s-line ones,i wont notice much of a drop..any help is appreciated.