Hey I currently have the Eibach Pro Street S coilovers. How much of a difference in stiffness of the ride will it make to add a 19mm HR rear sway bar from just running coils?

 

I do not have the coilovers but the H&R 19 mm RSB (soft setting) feels like it made the ride harsher by only 15-20% on bumpy roads but made a very significant difference on handling, lane changes, fast corners and bends.