They don't. Headers are really only worth it if they are full length. Mid/short length headers generally show little to no increase over stock manifold setups. And they way yours are designed are almost worse.
As for ground clearance I wouldn't worry. The front of my car is lowered too. Low enough that if I turn a corner too fast with a friend in the car. You can hear the tire rub the fender. And I still haven't hit anything with my full length under steering headers. That said. If you're worried about clearance. Dougs or tti are your best bet. They tuck up under the steering better. And won't be more than a 1/2 lower than the transmission pan from what I hear.
