ok? so y is it pointless to bolt on 7.7 WHP on a civic EX? y is header bad for a SOHC but good for the DOHC??

i have read that the LandSpeed PowerCore anD DC sports headers are great 7+ hp in 96 civic EX with pretty high mileage
http://www.turbomagazine.com/tech/0108tur_landspeed/

also hear is the comparison for most of the Available Header's for D series Civics
http://www.hadamotorsport.com/tech/review/dsemc/

BUT again please tell me y it isnt worth it?
because in the full article they said that highway driving was a lot better, didnt have to downshift to accelerate even driving up a fairly steep hill in 5th gear.

so i really dont understand how it isnt worth it. Most people spend more on an exhaust for 2whp then they would for a good header for 7whp.