I just intalled koni yellows with Tein H.Tech springs... and it's nice. it's just little drop, but in the front, it's noticeable. Before, I was able to put 4 fingers between the tire and the fender. Now it's barely 2... in the back, it's just a slight drop, and the wheel gap is now just little more than 2 fingers.
The ride is still smooth... even when I adjust the koni's (you can adjust them from smooth to firm in 5 minutes, easy) to be firmer, it's still good. oh yeah, it's more fun to drive!
if you want to go lower (depends where you live and the tires you have), go with Eibach pro kit with Koni yellows, and put the springs to the lowest perch on the koni's in the front. it will give you 0,5'' lower. I cannot do that... I live in Montreal and I have 225/40ZR18 tires/wheels. even with the H.Tech installed at the lowest perch on the koni's, I had rubbing issues in the front.