bilstein black are standard o.e replacements and yellow are the sport versions. As far as I'm aware bilstein don't make there own springs and if they come as a sport kit with black shockers it's not really a sport kit (shockers are not shortened so you loose some ride comfort as they will be mid way through there compression)
I can say eibach springs are good (I had some -40mm sportline versions) and the recomended shocks are boge (eibach use these to develop there springs)