The bar is cheap...but the labor to install is probably hard as you must lower a bunch of the rear suspension to install the bar...as I have heard. And, yes, more and larger anti-roll bars create a more responsive automobile up to a point. If you go too stiff on springs/shocks/roll bars/tires...you lose compliance on everyday roads and the darn thing doens't handle worth a damn on anything but the smoothest race track or street. But anything AMG puts out probably is a good trade of as to handling/performance...so you should not worry....it won't screw up your car.
Regards
Regards