it's not a V6 is it? doesn't look like it from your avatar.
try a 'search', there's plenty of info about the various products. but i'd recommend Eibach Pro Kit springs. alternatives would be H&R (bit stiffer i believe), Novitec or KONI.
as a result of lowering, you'll probably find the car 'underdamped' (ie: factory dampers lack the body-control you may want, resulting in too much crash and bounce). so i'd highly recommend upgrading the dampers too, to say KONI Sport, KONI FSD, or Bilstein B6.
or a good 'complete set' could be the Eibach Pro System (springs+dampers).
at the premium end, you have coilovers, like KW, Novitec, or Autodelta.
i personally run Eibach + KONI Sport, a combo i've had on other cars too, and find it a great compromise between cost, performance, lowering, and ride comfort (note: the Eibach springs do not lower the front of the V6 from standard height, so this requires modification to do so).
