Are you pushing 500 horsepower and/or 500 lb.-ft. of torque? If not, you are likely wasting your money on beefier control arms. A good set of standard control arms with good bushings will work fine on a practical street driven car.
Some guys like to weld some steel plates between the runners on stock arms to stiffen them up. Again, if you're building a road worthy cruiser with a stock or mildly hopped up engine, you'll be fine with the stock arms.
That's my nineteen cents worth.