First an internal combustion engine is little more than a big air pump.
Increasing the input and output devices and you WILL see an increase in performance.
There are a lot of things in between the intake and exhaust that could be tweaked but IMHO header are the best gain for the bucks and ease of install.
That said, add the header, then the intake increase (air tube, throttle body, etc), then think either higher lift rocker arms ( a little more advanced but still a bolt on ) or a new cam.
As to which brand, sorry I need to look at that myself, that is if I am stuck with the 3.0L.
Just make sure if you need emissions acceptance you get headers that do that too.
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