when you lower your car with springs, it is best to get new shocks that accomodate, take into consideration the lowering.
you want new, longer lasting shocks that are caliprated differently so you don't have the 'floaty' ride, especially at highway speeds. you also want to take advantage of the tighter ride which allows for better cornering as well.
which is why I have Bilstein Sport shocks. I initially lowered my car w/o the shocks and had to go back in later to do it. makes a big difference....good luck!