Spring rate of 503 lb/in front and 391 lb/in rear (9kf and 7kf) - stiff enough for spirited driving and for daily driving on smooth roads? What would be a better setup for spring rates that would give a good mix b/w performance and comfort? Thanks.

 

I'm wondering the same thing. I'm running 400lb/350lb now and about to go stiffer. I don't do smooth tracking but instead bumpy parking lot auto-x. Also Chicagoland roads are some of the worst anywhere so I must deal with potholes, ruts, etc.