Dude, no.
First of all they are all uglier than stock, or equal I guess in some cases... (like that black one you posted... not ugly but not great either)
You are talking about downforce... Seriously man, the cars that these kits are made for do NOT need downforce. This is something that many casual race fans don't understand. DOWNFORCE IS DRAG UNLESS YOU ARE LITERALLY ON THE EDGE OF FLYING OFF OF THE ROAD.
Most of these kits which include all this downforce are economy cars. The last thing they need is downforce.
EDIT: to take out the images so A7 doesn't mail me a bomb.