Used Koni shocks plus Ground Controls with 500f & 500r for ITR. This is a good suspension setup I believe, but what about the spring rates?
I dont think it will be too bad, since the stock ITR spring rates are the same front and rear(after the progressive part). Should the handling be like the stock suspension but stiffer? It is not super cheap, Its just in my hands at the moment and cheaper than if I were to buy them new.

 

I just got GC's and Bilstiens... 400/500. It is really stiff, but streetable. The is going to be a really big difference from stock. I am into it for $800 new.

 

streetable is good. But how is the handling going to be like with the rates the same?
It seems a lot of people like it stiffer in the rear than the front, but all the Japanese "coiloiver kits" have it stiffer in the front, sometimes way stiffer in the front than the rear.

 

Handling will be great at 500/500. It should give you a very neutral feeling, which is good. Higher rate in back = more rotation. Higher in front = more push. The Japanese do things (and drive) a bit different, plus understeer is always safer than oversteer, hence the stiffer front springs.

Now 500lb springs being "streetable" is another matter altogether. If this is your daily driver, you'll soon start to get tired of such heavy rates. If it is a weekend car, you'll be fine.