I HAD the sedan rear bar..it didn't eliminate enough understeer for me. So, I ended up with the Cusco adj bar and set it to 22 mm. That almost completely eliminated my understeer. Along with the other things done to my car.
Of course it help that I got the Cusco bar for free. BUt if your cost constrained, I don't see why the Whiteline wouldn't work.
I might try a 23 or 24 mm setting some day and see how the car reacts.