I had Eibach Sportlines in my old 325. Loved them, perfect height and great handling even on stock shocks. Apparently the rear shocks went shortly after I sold the car so keep in mind that you'll be up for shocks at some point (the springs were in the car for at least 60,000kms / 2 years before the rear shocks went).
H&R also make a good springs as well. I reckon you're best off sticking with German seeming they are specifically made for these cars and with handling in mind, mind you I've never tried King springs so I can't comment from first hand experience. I think King springs are only available in Australia - I've never seen them for sale on US websites so consider the R&D they would've gone to for the size of the e46 mod market over here.