Well a lot of your ride quality will depend on your shocks. What are you planning in that department?
I would look into either Koni or GAZ. As far as spring rates go, i would shoot pretty close to the H&R race springs - maybe a tad lower. From what i've heard, with the appropriate shocks, those rates are ok for a daily driver. (so around 325f 375r) but if you go any lower on the spring rates, I would be hesitant to lower the car any more than 2 inches.