Well, here's what I know, which may not be what you want to hear:
1. Yes, I would replace the headers, I had the same issue on mine and ended up cranking on the torsion bars to lift the front end up (the bonehead who owned it before me had the car all the way down....way down). I've been told that even though it wont' hurt your engine, it certainly doesn't help performance having one tube getting more backpressure than the others.
2. I've also been told that the X pipe is the way to go. I'm not sure that straight pipes are hurting your performance because I don't know what you have done to your motor.
3. I've got purple hornies on my car. If you're looking for loud, that's the way to go.