30 isnt mega low...and you will only really notice a diffrnace if your looking for it! it will be about 2inch lower over standard.. i used 35mm g-max on mine and you couldnt tell it was lowered with 15" alloys on until you looked under the archs, or was in the car...
my main concren about springs is handling. going low doesnt bother me, will admit it makes it look better.
