When I was looking at coilovers Ben I noticed Bilstein listed the pss10's with the same part number across the platforms, whereas KW gave them different ones.
The shockers are the same though as long as they are 55mm on the front, its just the spring rates differ on the KW's
No idea why the 4wd and 2wd are different unless its down to the rears having drive shafts and or extra weight , I've only had 4wd A3/S3's so I've never seen the 2wd setup.
Best bet is to check out the part numbers on the manufacturers site.
I ended up going with KW clubsports, all I can say is.......Awesome!