On the standard beam the toe changes quite a bit during bump and droop, causing the rear suspension to steer in the same direction as the front wheels. That makes that the car doesn't want to turn in that well. Your springs are quite stiff so the steering of the rear is less than normal. But I expect the 6 degree beam is still quite an improvement. Also the camber curves on the rear with standard beam on bump and droop don't match well with those of the front. With the 6 degree beam that is also better.

So yes I think it is worth the money.