I honestly don't think it's worth it unless you're tracking your car. They go through the middle of your trunk and make it so you can't have subs or put anything of any size in it.
Though if you do need that kind of control, it'll tighten up the rear nicely.
I'd assume the bavauto ones would be fine. If you pay money for some Racing Dynamics ones or something, the difference would be marginal and the price would be triple.