You sure you want that stiff feeling on your relatively new car? From what I've heard urethane bushings stiffen the car so much that you get that race car feel but it rattles everything. I have Eibach Pro Kit springs on my Spectra5 and I can take turns at 40mph in 4th gear with used up 20k miles on my Goodyear All-seasons. Good enough for me. Maybe consider spring upgrade for your KIA? Check out Kia
http://www.kia-fx.com/