[Hardder Performance]

I've got the dub air intake ,tbs, and corsa catback,,and (jet stage 2,,yes i know it suks but it didn't hurt) i want a better,,louder sound,,and hopefully more power!!
Does anybody have any experience to tell me about having those parts installed allready and then putting in the magnaflow cats??? do i need anything else such as a new o2 sensor or anything at all?? Could you tell if there is a louder deeper sound after installing the cats??? maybe a header hiflow combo??? but is new headers needed,i mean the car was desinged for pure power from the factory,,shouldnt the stock be enough as for the headers i mean.

pleas help,,aarrrgggggghhh
Thanx!!!!