Plus, spring rate != wheel rate. You have to take into account the motion ratios as well. On my car the front is about 0.95, and the rear is about 0.75. That means much stiffer springs in the rear just to get the same wheel rate (my stock rates are 129F/213R, my swift sport are 168F/252R, the Spec R's are 245F/296R).

I *think* the 04-07 has roughly equal motion ratios front/rear, so then it's just about shifting handling balance like Steve said.