A good place to post this would have been Chassis and Suspension forum.
There are many articles on springs there as well as in my shop forum.

Heavy spring rates are a poor substitute for anti-sway bars.
Anti-sway bars hold the car flat in a turn. Anti-sway bars can be tuned to
make the car handle to your driving style.

The stock spring rates were designed to support the weight of the car.
Unless you are coming down from being air born or racing on a banked track
where the weight of the car will "increase", stock springs rates will
support the stock weight of the car and allow the same type of handling
as the stock arrangement.

Making the front or rear springs "stiffer" will alter the handling and make either the front
or the rear hang out further in the turns. Some people call this tight or loose. Some people
call it understeer or oversteer.

Decide what you want the car to do for your particular driving style,
and let that be your guide.-Bob